Issue |
A&A
Volume 394, Number 3, November II 2002
|
|
---|---|---|
Page(s) | 1111 - 1116 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20021247 | |
Published online | 21 October 2002 |
Filling factors and magnetic field strengths of nanoflare-heated coronal active regions: Yohkoh and MDI observations
1
Department of Physics, UMIST, Manchester M60 1QD, UK e-mail: rjain@suraj.phy.umist.ac.uk
2
Center for Solar Physics and Space Weather, Catholic University of America, Washington, DC 20064, USA e-mail: yashiro@cdaw.gsfc.nasa.gov
Corresponding author: R. Jain, rjain@suraj.phy.umist.ac.uk
Received:
10
July
2002
Accepted:
26
August
2002
The scaling laws describing the relationship between thermal
and magnetic properties of active regions are derived using the concept that
solar coronal active regions are heated by numerous small flare-like events
(nanoflares). Thus, a coronal active region is viewed as an ensemble of
hot elementary filaments created within the coronal magnetic field by random
impulsive heating events. The scaling laws obtained are governed by the global
energy balance of the active regions
and are independent of the details of any heating process (such as the energy of
individual heating event or energy spectral index of nanoflares). We examined 61
coronal active regions observed with the soft X-ray telescope aboard Yohkoh
and found that such a model yields filling factors (defined as the ratio of the
volume of hot plasma to the total volume) in the range 0.002 to 0.015 and magnetic
field strengths of 20 G to 40 G. The analysis determining the mean magnetic field
strength and filling factors of a large number of coronal active regions, observed by
Yohkoh, based on nanoflare-heating concept is the first such analysis. We also
examine 24 active regions observed with the
Michelson Doppler Imager aboard Solar and Heliospheric Observatory and
find that the total thermal energy content Eth is related to the total magnetic flux
ϕ by a power-law index of 1.24 i.e. . The thermal
pressure pth of the active regions is related to the magnetic flux density
Bp obtained from MDI measurement as:
.
Key words: Sun: activity / Sun: corona / Sun: magnetic fields
© ESO, 2002
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