Table 1.
Comparison of the characteristic timescales calculated for the typical values of three coronal plasma non-uniformities in which rapidly decaying slow modes have been observed: warm quiescent loops seen in 171 Å (De Moortel 2009), coronal plumes seen in 193 Å (e.g. Krishna Prasad et al. 2014), and hot dense loops observed in the Fe XIX channel by SUMER (Nakariakov et al. 2019).
| Typical value | Loop in 171 Å | Plume in 193 Å | Hot loop in SUMER |
|---|---|---|---|
| (Symbol on plots) | (square) | (star) | (circle) |
| Temperature, T0 | 0.63 MK | 1.3 MK | 6.3 MK |
| Number density, ne | 1.5 × 109 cm−3 | 0.5 × 109 cm−3 | 1 × 1010 cm−3 |
| Period, P | ≈3−10 min | ≈8−18 min | ≈10−20 min |
| 𝒯M, B = ∞ | 3.2 min | 23 min | 23 min |
| 𝒯M, B = 34 G | 3.2 min | 23 min | 30 min |
| (β = 0.01) | (β = 0.00) | (β = 0.38) | |
| 𝒯M, B = 12 G | 3.3 min | 24 min | 81 min |
| (β = 0.05) | (β = 0.03) | (β = 3.0) | |
| 𝒯M, B = 4 G | 4.4 min | 29 min | 548 min ≃ 9 hr |
| (β = 0.43) | (β = 0.28) | (β = 27) | |
| 𝒯condB, B = ∞ | 10 min | 11 min | 27 min |
| 𝒯condB, B = 34 G | 10 min | 11 min | 36 min |
| (β = 0.01) | (β = 0.00) | (β = 0.38) | |
| 𝒯condB, B = 12 G | 11 min | 12 min | 97 min |
| (β = 0.03) | (β = 0.03) | (β = 3.0) | |
| 𝒯condB, B = 4 G | 14 min | 14 min | 650 min ≃ 11 hr |
| (β = 0.43) | (β = 0.28) | (β = 27) | |
| τrad | 9.7 min | 60 min | 70 min |
Notes. The three points (T, ρ) are marked on the plots in Fig. 1, and are the same parameters used for the three plots in Fig. 2. The characteristic timescale 𝒯M is calculated using Eq. (20) for heating model ℋ = ρ1/2T−7/2. The thermal conduction damping time 𝒯condB is calculated from Eq. (21) using wavelengths λ = 22 Mm, 100 Mm and 250 Mm respectively. A range of magnetic field strengths (hence β) are presented. The characteristic radiative timescale τrad is calculated from Eq. (29).
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