Free Access
Issue
A&A
Volume 569, September 2014
Article Number A32
Number of page(s) 13
Section Catalogs and data
DOI https://doi.org/10.1051/0004-6361/201321344
Published online 15 September 2014

© ESO, 2014

1. Introduction

Since the discovery of cosmic rays (CR) a century ago, instrumental capabilities have steadily improved. A large variety of types of experiments (balloon- or satellite-borne experiments, those flown on a shuttle, those installed on the International Space Station, or ground-based experiments) and techniques have been used (nuclear emulsions, drift chambers, Cerenkov counters, spectrometers, etc.) to refine our knowledge of the CR composition and spectrum.

The presence of heavy Z < 30(Freier et al. 1948a,b) and extremely heavy Z ≥ 30 elements (Fowler et al. 1967; Blanford et al. 1969) in the cosmic radiation were among the main discoveries related to Galactic CR nuclei, which culminated with the discovery of a few Z > 90 events (Fowler et al. 1970; O’Sullivan et al. 1971; Price et al. 1971). Isotopes and, in particular, the radioactive CR clocks were identified with more or less difficulties due to their decreasing abundance and mass separation with increasing atomic number: 10Be (Webber et al. 1973c), 36Cl (Young et al. 1981), 26Al (Webber 1982), and 54Mn (Webber et al. 1979). The CR leptons were identified in the early 60’s with the first measurement of electrons – also called negatrons at that time – (Earl 1961; Meyer & Vogt 1961) and of the positron fraction (de Shong et al. 1964; Hartman et al. 1965; Agrinier et al. 1965; Daniel & Stephens 1965b). Anti-protons are ~10-4 times less abundant than protons and were only observed in the late 70’s (Bogomolov et al. 1979; Golden et al. 1979). Anti-deuterons, which are expected to be yet another factor ~10-4 below (Chardonnet et al. 1997), are still to be detected: the best limit is given by the BESS balloon (Fuke et al. 2005; see also Abe et al. 2012a for limits on anti-helium), and is still three orders of magnitude above what is required to reach the expected astrophysical production. This level could be within reach of the AMS-02 detector on the International Space Station (Arruda et al. 2008; Choutko & Giovacchini 2008) and/or the GAPS balloon-borne experiment (Aramaki et al. 2012). We note that other milestones in CR studies are the discovery of the γ-ray diffuse emissions that were reported first by Kraushaar et al. (1972) and studied by the contemporary Fermi-LAT instrument (Ackermann et al. 2012b), and the first evidence of high-energy CRs from extensive air showers (Auger et al. 1939), which are currently studied at the Pierre Auger Observatory (e.g., Abraham et al. 2010).

In the last twenty years, a lot of effort has been devoted in measuring the CR composition at higher energy (TeV). Very accurate isotopic data were also provided in the low energy range ~100–500 MeV/n (Voyager 1 and 2, Ulysses, and ACE), over an extended period of time. The recently installed AMS-02 experiment on the International Space Station (May 2011) has started to provide impressive measurements in the GeV/n–TeV/n range (Aguilar et al. 2013). Interestingly, most of the even oldest CR measurements are not outdated yet. Indeed, many instruments are designed to focus on specific CR species: neither all instruments have the isotopic resolution capabilities nor have all species been measured repeatedly. Some old experiments are also useful when one wishes to inspect a possible charge-sign dependence (22 year cycle) of the Solar modulation effect as a function of the Sun polarity, as first proposed by Clem et al. (1996) and further studied in Clem & Evenson (2002). For all these reasons, we believe it is worth providing an archival database of CR measurements to the community.

The CR data are the backbone of Galactic CR propagation studies (e.g., Jones et al. 2001; Maurin et al. 2001; Strong et al. 2007; Evoli et al. 2008). In the last twenty years, anti-protons and positron fraction measurements have also become a strong probe for dark matter indirect searches (e.g., Porter et al. 2011; Lavalle & Salati 2012). A database would therefore be useful to any researcher in these fields but also to CR experimentalists, who wish to compare their data to previously published ones. Another independent effort to provide a CR database was presented in Strong & Moskalenko (2009). We present a contextualised and more complete version of the data here1, along with many user-friendly interfaces and tools to use them.

The paper is organised as follows: Sect. 2 describes the database content; Sect. 3 describes the website and available tools. We conclude and comment on possible improvements of the database in Sect. 4. Appendix A provides the rules to combine CR quantities from a given experiment (e.g., to form quantity A/B from A and B fluxes), and Appendix B gives a summary list of all the experiments/references contained in this first release.

2. Content of the database

In this section, we first describe the information gathered in the database and the data themselves. We then present how this information is organised in a MySQL framework2.

2.1. Definitions

The CR data are connected to experiments, analyses, and publications. The first step for creating the database is to define what an experiment is. Then, the need to define a sub-experiment arises because i) an experiment may consist of several detectors; or ii) an instrument may have flown several times, or over distinct periods. Data from a sub-experiment often involve several CR species, the analyses of which are published in one or several papers. For the sake of clarity, the following keywords/definitions are used in the database:

  • Experiment.

    Name associated with the instrument (CREAM, AMS). To identify unnamed balloons, we use the syntax Balloon (YYYY), and a further distinction is made if a balloon was flown several times: a comma-separated list of years Balloon (1966,1967) is used if the data were analysed and published for each flight; a plus-separated list Balloon (1967+1968) is used if the data resulted from the combined analysis of the flights3.

  • Sub-experiment.

    Sub-detector name or experiment name concatenated with the flight number and data taking period (YYYY/MM) with start and stop dates separated by a hyphen for durations over a month4: Balloon (1972/07), CREAM-I (2004/12-2005/01), CREAM-II (2005/12-2006/01), and Ulysses-HET (1990/10-1997/12).

  • Cosmic-ray quantity.

    Combination (sum, ratio, etc.) of measured CR species5. It can be an elemental (e.g., C), isotopic (e.g., 1H), or leptonic (e.g., e) flux, or any ratio of these quantities such as B/C, 10Be/Be, e+/ (e + e+), etc. The keyword SubFe is used for the group Z = 21−23, but no other charge group is defined for now.

  • Energy axis.

    Detectors often measure the CR total energy Etot or rigidity ℛ = pc/Ze (p is the momentum, Z the charge, c the speed of light, and e the electron charge). Data are also very often presented as a function of the kinetic energy Ek = Etotm (m is the CR mass) or the kinetic energy per nucleon Ek / n = Ek/A (A is the atomic number). In the database, we allow four representations of the energy unit and axis: [GeV] for Etot, [GV] for , [GeV] for Ek, and [GeV/n] for Ek / n.

  • Publication.

    Refereed or non-refereed reference (i.e., journal or conference proceedings) providing CR quantity data from (sub-)experiments. A publication is usually attached to a single (sub-)experiment, and it contains different CR measurements, but there are a few exceptions. Over time, some of these publications may be superseded by newer analyses: a specific entry of the database allows us to keep track of deprecated analyses and references.

  • Data.

    The CR quantity measurement and uncertainties at one or several energy bins (see Sect. 2.2 for a complete description).

Because the combinations of CR quantities are themselves CR quantities, this introduces a subtleties in the choice of how to handle the database. One could be tempted to fill the database with all useful combinations of data (e.g., the often used B/C ratio) from published quantities (e.g., B and C fluxes). However, the number of combinations that can be formed is large (for Z < 30, as many elements and about a hundred isotopes can be combined), and the procedure to combine the errors on the measurements is not always sound. For these reasons, we decided to fill the database with the published quantities only. We leave the task of extracting the most complete dataset (for a given CR quantity) to the Data Extraction tab interface (Sect. 3.2), which combines the data found directly in the database and those obtained by looking for all combinations of data leading to this quantity (see Sect. 3.2 and also Appendix A for a discussion of the priority rules and criteria to decide how and when to form new quantities and evaluate their uncertainties).

2.2. Data description and units

The structure of a CR data entry (energy, energy range, measurement and uncertainties) for any measured quantity is as follows:

  • E

    “Central” energy given in the publication (unit is [GeV] if the energy axis is Etot or Ek, [GV] for , and [GeV/n] for Ek / n). If only the bin range (see below) is given in the publication, the geometric mean is used.

  • Bin range

    Energy range (same unit as E). If only E is given in the publication, Emin = Emax = ⟨ E.

  • Value

    Measured CR quantity in unit of [(⟨ E ⟩ m2 s sr)-1] if this is a flux, or unitless if this is a ratio. The data correspond to top-of-atmosphere (TOA) quantities, which is modulated by the Sun’s activity.

  • Stat Err

    Statistical error (same unit as Value).

  • Syst Err

    Systematic error (same unit as Value); this is set to 0 if not given in publication.

In the database, these values must be filled for each data point from the published data. Whenever available, we used the values given in the publication tables. However, most publications provide none, and the data had to be retrieved from the plots (using the DataThief III software6).

2.3. Solar modulation description

A flight period for a given instrument is uniquely associated to a Solar activity period. For each sub-experiment of the database, a unique modulation level thus can be attached. In practice, its determination depends primarily on the choice of the (unknown) Solar modulation model. It also depends on the assumption made for the unknown interstellar (IS) flux and on the set of data used for its calculation. At least three different model-dependent approaches exist: the modulation potential given in the experimental papers is very often determined from an assumed ad-hoc local interstellar spectrum (LIS), which is modulated to match the data. Another widely used approach is to take a demodulated spectrum from another publication and modulate it to match the data. Another strategy is to rely on the worldwide network of neutron monitor data that gives an indirect estimation of the Solar modulation level (Usoskin et al. 2002, 2005, 2011).

2.3.1. Sets of modulation levels in the database

As there is no consensus yet regarding how to proceed best, we provide several sets of values (of the modulation parameters) in the database and the underlying assumptions made for their determination. The two sets introduced in CRDB V2.1 are

  • 1.

    From publication: in this set, the solar modulation values are directly taken from the publications. This set is not homogeneous, since each value relies on IS fluxes and Solar modulation models (see below), which differ from one publication to another. We note that the underlying hypotheses are not always provided and that only a small fraction of the publications offers a modulation value at all.

  • 2.

    NM [Uso11]: the modulation levels in this set (φ in the Force-Field approximation) are based on the NM data analysis of Usoskin et al. (2011). Monthly average values in the period July 1936 – December 2009 are interpolated for the flight dates of each sub-experiment. The ensemble of values forms a homogeneous set of φ for all sub-experiments, because each value is based on the same modelling.

It is very important to pursue the efforts towards the determination of homogeneous sets of modulation parameter values: (1) because these values are routinely used as is by cosmic-ray physicists for CR propagation studies (and also in the context of indirect dark matter detection) and (2) because assessing which is the correct modulation model requires to disprove simple models. Systematic studies of CR data on several decades are mandatory to achieve this goal. Indeed, as underlined in Maurin et al. (2014), there is a degeneracy between the IS flux and the solar modulation level: assuming the wrong IS flux lead to a shift of all determined φ values. Combining the results of direct fits to CR data and the use of NM data should provide more robust (and homogeneous) determinations of φ time series (Maurin et al. 2014). As progress is made along this line (Ghelfi et al., in prep.), new sets of values will complement the two above.

2.3.2. Ingredients: Modulation model, IS flux, and data

The modulation level for any set and any sub-experiments is associated to assumptions regarding the ingredients of its calculation. To avoid too much complexity, a few general categories were created for each ingredient:

Examples of how these informations are organised and displayed in CRDB are given in the next sections.

thumbnail Fig. 1

Tables and keys of the database MySQL structure (see text for details).

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2.4. Database structure description

The database engine is MySQL5, hosted at the Laboratoire de Physique and Cosmologie (LPSC) on a backed up server. The structure and keys are shown in Fig. 1 (keys in exp,subexp, and publi were discussed in Sect. 2.1, those in data are found in Sect. 2.2, and those in ref_modulation_type in Sect. 2.3). Each entry in a table is associated with a unique identifier. These identifiers are used to link elements from one table to another (for example, several sub-experiments can be linked to a single experiment). For completeness, all tables of Fig. 1 are briefly described below:

thumbnail Fig. 2

Snapshot of the Experiments/Data tab content (Sect. 3.1). The help box is activated by clicking on the [question mark] icon and a picture of the instrumental setup (not shown) pops-up when clicking on the [magnifying glass] icon. The Instrument description box appears for a mouse-over action on the sub-experiment name. A click on [data] pops-up a new window with the data entries and a summary of all the (sub-)experiment/publication informations (not shown).

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  • exp Name, type, web site (if available), and flight date.

  • subexp Link to which the experiment belongs, name, description of the apparatus, flight details (launch place and the number of flights for balloons), flight dates, distance to the Sun [AU], and Solar modulation level [MV].

  • publi Bibliographic reference, web link, publication year, Bib10 entry (taken from the Astrophysics Data System ADS11), and link to other publications (if more recent analyses exist).

  • subexp_publi Bridge table linking entries from publi to one or several entries of subexp.

  • phi Solar modulation level and error for the sub-experiment.

  • ref_modulation_type Bridge table linking entries from phi to entries in the three tables below.

  • ref_IS_flux List/description of IS flux categories.

  • ref_modulation_model List/description of Solar modulation models.

  • ref_data List/description of data used to calculate φ.

  • element Name, mass, atomic number, charge, etc. for CR quantities (isotopes, elements, , e, and e+).

  • data Type (flux or ratio of element), energy axis, energy, bin range, value, statistic and systematic errors.

  • abondance Association of each element to its most abundant isotope to allow (approximate) conversions between different energy axes (since V1.2).

  • user Contact details of administrators (persons authorised to change and validate submitted data).

  • log Statistics of the number of the users (since V1.2).

  • validation Contact details of persons submitting new data (see Sect. 3.3 for the New Data interface), validation date and Identity of the person (user) who validated the data.

3. Website, interfaces, and example plots

The CR database website (http://lpsc.in2p3.fr/crdb) is hosted by the LPSC laboratory website and is based on a LAMP solution12. Authentication uses the https protocol to ensure a good level of confidentiality. (Only administrators use their own credentials to access protected areas.) All web pages are written using the PHP (Hypertext PreProcessor) language, with a global structure made in AJAX (Asynchronous JavaScript and XML). The third-party libraries jquery, jquery-ui, jquery.cluetip, and table-sorter are also used.

The website is based on tabs, in which the user is guided by help boxes (identified by [question mark] icons). We give below a brief description of the implemented tabs:

  • Welcome Quick description and organisation of the database, log of the latest changes, and link to download the database content formatted for the USINE13 propagation code.

  • Experiments/Data List of available data sorted by experiment names or dates. A list of experiment acronyms is given.

  • Data extraction Main interface to retrieve data in ASCII files, ROOT14 macros and plots, and Bib references for the selection.

  • Admin Shown for authenticated users only: internal checks of the database content and validation of submitted data.

  • Links Standard useful (here GCR-related) web links.

  • New Data Interface to submit new data which will appear in the database after validation by authorised users.

thumbnail Fig. 3

Snapshot of the Solar modulation values for a given sub-experiment (after clicking on [data], see Fig. 2, then [Parameters]).

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As underlined previously, native data (i.e., data directly from publications) are listed and accessed from Experiments/Data (Sect. 3.1). In the Data extraction tab (Sect. 3.2), native data and matching combinations of native data are combined to provide the most complete list of data found for user-selected quantities/criteria. Adding new data is possible from the New data tab (Sect. 3.3).

3.1. Data access from EXPERIMENTS/DATA tab

thumbnail Fig. 4

Snapshot of the Data extraction tab interface. In the upper panel, a CR quantity is chosen by means of selection boxes (auto completion enabled). In the lower panel, more search criteria are possible (energy range, list of experiments or sub-experiments, time period, etc.). The selector [Solar modulation evaluation] allows the user to choose which set of φ values (see Sect. 2.3) is displayed. A tick box allows to add in the search the data points obtained from combinations of “native” data (see Appendix A). Clicking on the [Extract selection] button pops up the results, as shown in the example Fig. 5.

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Figure 2 shows a snapshot of the Experiments/Data tab (and some enabled actions within this tab). The list of published data is ordered by experiment name or date. For each experiment, the list of sub-experiments is shown and sorted by start time15. The publication references related to this sub-experiment are then listed, along with the quantities measured (older analyses/publications of the same data are indicated). The most useful actions/pop-up informations available for the user are as follows:

  • experiment description (name, type, official web page);

  • sub-experiment description (name, data periods16, instrument description [mouse-over] name, experimental setup picture [magnifying glass] icon);

  • data for each publication (from a sub-experiment). A click on [data] (see Fig. 2) pops-up a window (not shown in the examples): its upper half summarises all the information on the sub-experiment (contained in the database) and gives the ADS link of the reference. The lower half shows the data (see Sect. 2.2 for their format): ratios are sorted first and fluxes second. (One can jump directly to the data of interest clicking on one of the quantities suggested in the upper half panel.) In the upper half panel, clicking on [Solar modulation: Parameters] pops up a new window with the sub-experiment modulation values, as shown in Fig. 3. [Solar modulation: Parameters]).

By default, CR data for nuclei and anti-nuclei are given as a function of kinetic energy per nucleon, whereas leptons are given as a function of the kinetic energy. Whenever the energy axis for a given dataset is given as a function of rigidity, the flag “Rigidity” (in red colour and in brackets) is added after the data.

thumbnail Fig. 5

Snapshot of the result of the Data extraction operation. This pop-up window appears after the selection step shown in Fig. 4 is completed. Buttons, links, and tables give access to raw data and plots, see text for details.

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3.2. Selection and tools from DATA EXTRACTION tab

Figure 4 shows a snapshot of the selection interface within the tab. A mandatory step is the quantity selection (Flux or ratio selection), for which a few predefined choices are proposed. For a ratio, both the numerator and denominator selection boxes must be filled (auto completion is enabled). The other optional selection criteria (Refine search criteria) are:

  • Energy axis: to be selected among EKN, EK, R or Etot17;

  • Flux rescaling: multiplies the flux values and errors by Ea (useful for presentation purpose);

  • Energy range: restricts the energy range allowed;

  • (Sub-)Experiment names: list of comma-separated names (partial names allowed, e.g., CREAM, BESS);

  • Time interval: selects only experiments falling into the selected period (format is YYYY/MM);

  • Show also data from combinations: tick box to add in the search the data points obtained from combinations of “native” data (see Appendix A).

Hitting the [Extract Selection] button pops-up a new window with the data extracted from the user selection. This is shown in Fig. 5, which is organised in three panels (click on [hide]/[show] to collapse/expand each panel):

  • 1.

    Plots and exports for the selection:

    • Export selected data in various formats: [Get Data Files], [GET USINE/GALPROP File] provide a tar-ball of ASCII files containing the data (one file per sub-experiment) and a USINE- or GALPROP-compliant file (i.e., input for these propagation codes) respectively;

    • Exports plots: [Get ROOT Macro] and [Plot] provide a ROOT executable C++ file to re-generate and/or modify the plot19 and a high-resolution image database_plot.png respectively;

    • [Replot] (since V1.2): new panel to change the plot (size, y-axis range, select only a subset of sub-experiments, etc.).

  • 2.

    List of experiments found for the selection: summary of the data sorted by (sub-)experiment (name, publication, number of data, etc.). The [Get Bibtex] and [Latex cite] buttons provide a Bib file (bibtex.bib) to be included in the references, and the text to cite this selection in the document18. As for the Experiments/Data tab (Sect. 3.1), links to the experiment website and the ADS publication are provided.

  • 3.

    Data for the selection: data in a table (see Sect. 2.2 for the content description) sorted by experiment name or energy. An asterisk denotes the data obtained by combinations of native data of the database (see Appendix A).

With the default search criteria (i.e., none), we note that all analyses of a CR quantity by the same instrument show up in the result as long as they correspond to different data taking (or analysed) periods (i.e., different sub-experiments). For most of the time, these data are independent, but the analysed periods overlap in a few cases. It happens, for instance, for the Voyager data (launched in 1977 and still taking data). In that case, it is up to the user to decide, which data sets are relevant for her/his analysis, and exclude it using the “Sub-Experiment” or “Global Time interval” selection boxes (see Fig. 4).

3.3. New data from the ADD DATA tab

This tab allows anyone to interactively enter new data. This is an essential part of the database as it provides the community with the possibility to contribute to the completion of the database (either by adding data from new instruments, or adding missing data from older experiments).

thumbnail Fig. 6

Snapshots of the user interfaces in the Add data tab. The first stage for adding new data is the submitter identification (upper panel). The ordered four-step submission process comes next (middle panel). The user has to either select among existing entries or insert a new one (this pops-up a window with fields to fill), which does not work for the fourth step that concerns the CR data. The latter must be filled one CR quantity at a time (and must belong to the list of quantities declared at the publication step): the bottom panel shows the state of the panel once this step is reached with the energy axis to select, the data file to upload, and the [Graphical check before submission]. We note that help buttons exist for most of the fields to fill at all steps.

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Submitting new data consists of two parts: as shown in Fig. 6 (top panel), the first part concerns the submitter identification (contact details). The second part (same figure, middle and bottom panel) is data submission. Four steps must be passed in order. For the first three steps (experiment, sub-experiment, and publication), the submitter is left with the choice of selecting her/his entry among those already in the database, or to add a new entry ([Insert new] button): the latter action pops-up a new window in which the submitter is guided, where help boxes are provided for each item, to fill the necessary information, which match the keys of the database structure as described in Sect. 2.4 (see also Fig. 1). Each time a new entry is submitted, the submitted element becomes available for further submissions, though it does not appear yet in the database (i.e., in Experiments/Data and Extract data tabs).

Once the three previous steps are completed, the last action is the submission of the CR data (see bottom panel of Fig. 6). A template file for the required format (and units) of the data is provided (see Sect. 2.2). Only one CR quantity at a time (with as many energy bins as desired) can be submitted. Before the final submission of the data, the [Data graphical check] button pops-up a summary of the uploaded file, along with a plot of the submitted data for a last visual inspection. At this stage, the submission process can still be cancelled if any mistake is spotted.

For each submitted entry (experiment, sub-experiment, publication, and data), an email is sent to the administrators of the database content20. Validation tools from the Admin tab are then used (format check, completeness, etc.) to authorise the addition in the database (pending validation, the data are inserted in the database with a “not validated” flag and do not appear on the web site).

4. Conclusions and future improvements

We have developed a database of charged CRs (http://lpsc.in2p3.fr/crdb) that includes e, e+, , and nuclide data up to Z = 30 for energies below a few TeV/n. Each CR data is linked to a description of the instrument that measured it (flight dates, picture of the experiment setup, techniques used, etc.) and to the ADS reference in which it was published: this first release contains more than 200 experiments and 200 publications. The data can be extracted according to a selection on the CR quantity, the energy range, the experiments, and the epoch of measurement: ASCII files, ROOT macros, plots, and Bib TeX for the corresponding publications are then readily available. Since CRDB V1.3, we have also implemented (on request) a REST interface21.

The possibility to add new data by means of a user-friendly interface enables the database to be a collaborative tool for the CR community, provided enough people take an interest, use it, and help expand it. New data will be added as new results become available (We encourage experimentalists to submit their data once they become public.). The database could also be extended to a larger energy domain (data from ground-based detectors TeV/n data) or to heavier species (Z > 30). Time series, such as low-energy proton, helium, and electron data with a monthly or finer time resolution from long-lived high-precision instruments (e.g., AMS-02) could also be very interesting inputs for Solar modulation studies.

We welcome any help to further develop the database. Comments, questions, suggestions, and corrections22 can be addressed to crdatabase@lpsc.in2p3.fr.


1

The data were gathered independently of the data presented in the Strong & Moskalenko (2009) database https://sourceforge.net/projects/cosmicraydataba

2

The descriptions correspond to CRDB V2.1, which was the version at the time of re-submission of the paper.

3

The naming convention chosen for the experiment and the sub-experiment ensures the many unnamed balloons flown before the 90’s to be uniquely defined.

4

Some of the start and stop dates for balloon flights are not given in the publication and were taken from the StratoCat database of stratospheric balloons launched worldwide since 1947 (http://stratocat.com.ar/globos/indexe.html). For long-lived instruments, we do not include the excluded time periods (within the start and stop dates) in the database based on the analysis quality criteria (solar flares, high solar activity, instrument stability, etc.) because they are never given in the publication.

5

A CR must be a stable species with respect to the confinement time in the Galaxy, with an effective lifetime kyr (note that the electronic capture decay mode is suppressed because CR nuclei are fully stripped of e above ~0.1 GeV/n).

7

For the time being, only one parameter value per Solar modulation model is allowed. If no value is provided in the publication or if a 3D model is used, the value is set to 0.

8

The parameter φ is related to the Solar wind velocity Vw, the spatial-dependent diffusion coefficient κ(r), and the Solar cavity boundary R0 by . We note, however, that this formula depends on assumptions made on the wind spatial dependence and the diffusion coefficient rigidity dependence.

12

The acronym LAMP refers to a stack of free open source softwares: Linux operating system, Apache HTTP server, MySQL database software, and PHP.

15

We refer the reader to Sect. 2.1 for the definition of what is meant by experiment, sub-experiment, publication, etc., and to Sect. 2.4 for the structure of the data in the MySQL frame.

16

Full details of the flight dates are given clicking on [data]. The start and stop time format is YYYY/MM/DD-hh:mm:ss. A new line is used for each flight.

17

As already said, most data are published in EKN for nuclei and anti-nuclei and EK for leptons (very few data are published on several energy axes). For elements, a conversion to move from one energy axis to another is implemented, since V1.2. The result is approximate, since a unique A, Z, and m must be assumed for all isotopes of this elements. (We use the most abundant isotope, which is a very good approximation for some elements.)

18

These files are useful to quickly prepare scientific manuscripts based on and Bib. Appendix B and the references of this paper were prepared with the full list of references retrieved from the [Get Bibtex] and [Latex cite] buttons in the Welcome tab.

19

Based on the ROOT library http://root.cern.ch. To execute, type root database_plot.C (the data are hard-coded). The errors displayed correspond to the quadratic sum of statistical and systematic uncertainties.

20

For now, the only authorised persons are the developers of the database. Any person wishing to get involved in further developments of the database is welcome to contact us.

21

An example of call using a command line in an xterm is given by wget “http://lpsc.in2p3.fr/crdb/rest.php?num=C&energy_type=EKN” - -output-document=file. For a list of parameters, click on [REST interface] (Fig. 5).

22

Despite our best efforts, many data published in CR conferences (e.g., ICRC) are probably missing, and many typos and errors probably remain to be corrected.

23

The list and Bib references were obtained from the Get all Bib entries and cite links in the Welcome tab.

Acknowledgments

We thank our colleagues B. Coste, F. Donato, and A. Putze who contributed to the collection of some of the data gathered in the first release of this database. We thank A. Putze for useful comments on the paper. This work is part of the USINE project (CR propagation code). It has been financially supported by the PNHE.

References

Appendix A: Forming a new combination of data from “native” data in the database

The CR experiments provide measurements over several energy bins. The elementary brick of information in GCR physics is the isotopic flux. However, isotopic identification is rarely achieved even in contemporary experiments, and published results are often ratios of elements (e.g., B/C) and elemental fluxes (e.g., B, C).

Flux measurements suffer from many systematics (energy-dependent acceptance, dead time, rigidity cut-off in the Geomagnetic field, etc.) that mostly factor out from the ratio of species close in charge. As a result, uncertainties of published ratios are smaller than if calculated by quadratically combining the errors on the fluxes. Obviously, published ratios should always be preferred if provided in the publication. However as underlined in Sect. 2.1, only the most used ratios are generally published (e.g., B/C).

In this Appendix, we detail how “native” data are searched for and combined to lead to the user-selected quantity (Appendix A), as it is for fluxes or ratios. We then discuss the necessary rules to calculate the uncertainties from the “native” data uncertainties (Appendix A). We note that the data can only be combined if coming from the same sub-experiment. (Otherwise, they would correspond to different Solar modulation periods and suffer from different systematics.) Obviously, the benefit of adding extra data (for a CR quantity) to a CR analysis must also always be weighted against using only the “native” and more accurate data found in the same energy range. A check box in the selection interface (shown in Fig. 4) enables or disables the search for these data. We did not systematically check how many extra data points are obtained in this way, but the algorithm finds some. These data are singled out by an asterisk in the result panel (shown in Fig. 5).

A.1. Priority rules to form new quantities

The database extraction tool (Extract data tab) is designed to return the most complete set of data for a given CR quantity Qsearched. It needs a set of rules to browse through the database content and retrieve the queried quantity. The search is prioritised as follows (We use the superscript native to indicate quantity in the database.):

  • 1.

    look directly for the queried quantity Qnative;

  • 2.

    if Q is a flux, search for all i for which the pair (Q/Qi)native, (Qi)native exist. The new data obtained are Qcombo = ∪ i{(Q/Qi)native/ (Qi)native};

  • 3.

    if CR quantity is a ratio Q = Qnum/Qdenom, search for

  • ;

  • Qcombo = ∪ i{(Qnum/Qi)native/ (Qdenom/Qi)native};

  • Qcombo = ∪ i{(Qnum/Qi)native × (Qi/Qdenom)native}.

To be complete, more complex combinations should be implemented (addition and subtraction of isotopic fraction of an element, addition of group of charges, etc.). These combinations require a more complex query that remains to be implemented (it is under development).

Another subtlety is that valid combinations are restricted to data points of similar energy ranges. As underlined in Sect. 2.2, sometimes only the “central” energy bin of the data point is available. Moreover, values extracted from published plots (using DataThief) cannot match exactly one another. For these reasons, we relax the constraint of a perfect energy match and use instead

  • data point that haves only a “central” value: we demand this value to be i) within the energy range, or ii) within 20% of the “central” value of the data point it is combined to;

  • data point that have an energy range: we demand an overlap of the energy ranges of the data points to be combined.

A.2. Rules to calculate uncertainties

For all experiments, the default rule is that relative errors are quadratically summed whenever combinations of CR data are formed. In this first release, the only exception concerns HEAO-3 data (Engelmann et al. 1990), where the authors provide tables for the oxygen flux and for the relative fluxes (to O). The rules to calculate uncertainties depends on the charge proximity of the combined elements. The original text, which is spread over the original publication, is reproduced below:

  • “In Table 5 [...] the standard error is given with each flux value. This error includes the statistical error and, in the case of the last two energy channels, the systematic error.”

  • “The spectrum of any element between Z = 4 and Z = 28 can be obtained by multiplying the oxygen flux values of Table 5 by the corresponding abundance ratios given in Table 2. The relative errors on these two numbers shall be quadratically summed to get the error on the flux derived by this way.”

  • “For widely different charges Z 1 and Z 2 , a reasonable estimate of the error on the abundance ratio is the quadratic sum of the errors on both type of nuclei Z 1 and Z 2 (for example, the total error on Fe/O ratio is ~ 5.2%). For nearly adjacent charges, an upper limit of the systematic error is given by the difference between the systematic errors on each element (for example, the error on B/C is ~ 0.4%).”

Appendix B: List of experiments and publications

We provide below a sorted list of experiments (unnamed balloons appear first), sub-experiments, and associated publications present in the database first release23.

All Figures

thumbnail Fig. 1

Tables and keys of the database MySQL structure (see text for details).

Open with DEXTER
In the text
thumbnail Fig. 2

Snapshot of the Experiments/Data tab content (Sect. 3.1). The help box is activated by clicking on the [question mark] icon and a picture of the instrumental setup (not shown) pops-up when clicking on the [magnifying glass] icon. The Instrument description box appears for a mouse-over action on the sub-experiment name. A click on [data] pops-up a new window with the data entries and a summary of all the (sub-)experiment/publication informations (not shown).

Open with DEXTER
In the text
thumbnail Fig. 3

Snapshot of the Solar modulation values for a given sub-experiment (after clicking on [data], see Fig. 2, then [Parameters]).

Open with DEXTER
In the text
thumbnail Fig. 4

Snapshot of the Data extraction tab interface. In the upper panel, a CR quantity is chosen by means of selection boxes (auto completion enabled). In the lower panel, more search criteria are possible (energy range, list of experiments or sub-experiments, time period, etc.). The selector [Solar modulation evaluation] allows the user to choose which set of φ values (see Sect. 2.3) is displayed. A tick box allows to add in the search the data points obtained from combinations of “native” data (see Appendix A). Clicking on the [Extract selection] button pops up the results, as shown in the example Fig. 5.

Open with DEXTER
In the text
thumbnail Fig. 5

Snapshot of the result of the Data extraction operation. This pop-up window appears after the selection step shown in Fig. 4 is completed. Buttons, links, and tables give access to raw data and plots, see text for details.

Open with DEXTER
In the text
thumbnail Fig. 6

Snapshots of the user interfaces in the Add data tab. The first stage for adding new data is the submitter identification (upper panel). The ordered four-step submission process comes next (middle panel). The user has to either select among existing entries or insert a new one (this pops-up a window with fields to fill), which does not work for the fourth step that concerns the CR data. The latter must be filled one CR quantity at a time (and must belong to the list of quantities declared at the publication step): the bottom panel shows the state of the panel once this step is reached with the energy axis to select, the data file to upload, and the [Graphical check before submission]. We note that help buttons exist for most of the fields to fill at all steps.

Open with DEXTER
In the text

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