Fine details in solar flare ribbons - Statistical insights from observations with the Swedish 1-m Solar Telescope

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Table 2.

Riblet statistics.

	F1 (μ = 0.35, M4.6)	F2 (μ = 0.79, C8.3)	F3 (μ = 0.98, M1.8)
Number of 1 (2) peak RPs	3 (14)	4 (9)	14 (5)
Fraction of pixels labelled as 1 (2) peak	0.08 (0.92)	0.40 (0.60)	0.74 (0.26)
Riblet length^(a)	580–1500 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 79–1 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 99)	280–750 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 38–1 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 01)	N/A
Riblet width	110–330 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 15–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 45)	80–360 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 11–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 49)	110–310 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 15–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 41)
Riblet separation distances	200–450 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 35–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 61)	170–420 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 23–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 57)	200–280 km (0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 27–0 $\overset{″}{.}$ ${{\overset{\prime\prime}{.}}}$ 38)
Fitted amplitude^(b)^(c)	2.1–3.8	1.2–1.7	1.9–2.3
Fitted Doppler shift^(b)^(c)	16–32 km s⁻¹	13–44 km s⁻¹	2–21 km s⁻¹
Fitted line width^(b)^(c)	25–50 km s⁻¹	12–42 km s⁻¹	25–37 km s⁻¹

Notes.

^(a)

Projection effects are not accounted for when estimating the length of the riblets.

^(b)

The estimated range of the relevant parameter was computed by extracting the maximum and minimum of the FWHM of the distributions.

^(c)

For consistency between all three observations, the ranges were obtained from the fitting to a single-Gaussian curve only, as found to be necessary by the μ = 0.35 and μ = 0.79 flares. Additionally, fitted pixels that showed blue shifts were excluded.

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