Lower-ionosphere electron density and effective recombination coefficients from multi-instrument space observations and ground VLF measurements during solar flares

被引：6

作者：

Zigman, Vida ^{[1
]}

Dominique, Marie ^{[2
]}

Grubor, Davorka ^{[3
]}

Rodger, Craig J. ^{[4
]}

Clilverd, Mark A. ^{[5
]}

机构：

[1] Univ Nova Gorica, Vipavska Cesta 13, Nova Gorica 5000, Slovenia

[2] Royal Observ Belgium, 3 Ave Circulaire, B-1180 Brussels, Belgium

[3] Univ Belgrade, Fac Min & Geol, Phys Cathedra, Djusina 7, Belgrade 11000, Serbia

[4] Univ Otago, Dept Phys, POB 56, Dunedin 9054, New Zealand

[5] British Antarctic Survey UKRI NERC, Madingley Rd, Cambridge CB3 0ET, England

来源：

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS | 2023年 / 247卷

关键词：

Solar flares; Solar spectral irradiance; Ionosphere; VLF; Time delay; Electron density; EARTHS LOWER IONOSPHERE; D-REGION ENHANCEMENTS; AMPLITUDE; IONIZATION; ABSORPTION; CHIANTI; EVENT; PHASE; RATES;

D O I：

10.1016/j.jastp.2023.106074

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

A new model to predict the electron density and effective recombination coefficient of the lower ionosphere under solar flare conditions is presented. This model relies on space-borne solar irradiance measurements in coincidence with ground recorded active transmissions of Very Low Frequency (VLF), (<30 kHz) signals. Use is made of the irradiance measured by broad-band radiometers onboard the satellites: GOES, SDO, and PROBA2. Measurements are made over succeeding and partly overlapping wavelength intervals of the instrument band-pass ranges altogether covering the range 0.1-20 nm. The aim is to determine the effectiveness of the particular instrument bandpass in producing changes in the ionization of the lower ionosphere (D-region) during solar X-ray flares. Ionization efficiency is evaluated using modelled Solar Spectral Irradiance for each flare separately and for each instrument as a function of its bandpass.The new model is based on coupling of the continuity equation with the Appleton relation and uses the concept of time delay - the time lag of the extreme VLF amplitude and phase behind the flare irradiance maximum. The solution of the continuity equation predicts the electron density time -height profile for 55-100 km altitude.An analysis of M to X class flares shows the flare-enhanced electron densities due to a particular ionizing wavelength domain are in good agreement for the case where irradiance is taken over the bandpass of (1) either GOES (0.1-0.8 nm) or SDO/ESP (0.1-7 nm) for up to 90 km (2) either SDO/ESP or PROBA2/LYRA (1-2 +6-20 nm) at heights above 90 km. The results agree within 22% for heights up to 90 km, and differ by at most a factor of 2 for heights above 90 km. Remarkable agreement is shown between measured and evaluated time delay; discrepancies are generally less than 8%. The effective recombination coefficient is deduced from the model itself and is found to be consistent with other independent estimates.

引用

页数：15

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