Ionization increases associated with the small solar proton events of 5 February 1965 and 16 July 1966

Observations of partial reflections from the ionosphere at vertical incidence at 2.66 MHz have been made at Resolute Bay, geographic latitude 74.7 °N, since September 1963. By measuring the amplitudes of the ordinary and extraordinary backscattered waves information is obtained about electron number densities in the lower ionosphere. The results presented in this paper show that the partial reflection technique is more sensitive than most other ground-based experiments for the detection of D-region ionization increases associated with small solar proton events. Results obtained by the partial reflection experiment during the events of 5 February 1965 and 16 July 1966 are presented and compared with VLF and satellite observations.

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D-region electron density and effective recombination coefficients during twilight – experimental data and modelling during solar proton events

Annales Geophysicae ◽

10.5194/angeo-27-3713-2009 ◽

2009 ◽

Vol 27 (10) ◽

pp. 3713-3724 ◽

Cited By ~ 13

Author(s):

A. Osepian ◽

S. Kirkwood ◽

P. Dalin ◽

V. Tereschenko

Keyword(s):

Electron Density ◽

Zenith Angle ◽

Solar Zenith Angle ◽

Solar Proton ◽

Radio Waves ◽

Electron Densities ◽

Partial Reflection ◽

D Region ◽

Density Values ◽

Solar Proton Events

Abstract. Accurate measurements of electron density in the lower D-region (below 70 km altitude) are rarely made. This applies both with regard to measurements by ground-based facilities and by sounding rockets, and during both quiet conditions and conditions of energetic electron precipitation. Deep penetration into the atmosphere of high-energy solar proton fluxes (during solar proton events, SPE) produces extra ionisation in the whole D-region, including the lower altitudes, which gives favourable conditions for accurate measurements using ground-based facilities. In this study we show that electron densities measured with two ground-based facilities at almost the same latitude but slightly different longitudes, provide a valuable tool for validation of model computations. The two techniques used are incoherent scatter of radio waves (by the EISCAT 224 MHz radar in Tromsø, Norway, 69.6° N, 19.3° E), and partial reflection of radio-waves (by the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E). Both radars give accurate electron density values during SPE, from heights 57–60 km and upward with the EISCAT radar and between 55–70 km with the partial reflection technique. Near noon, there is little difference in the solar zenith angle between the two locations and both methods give approximately the same values of electron density at the overlapping heights. During twilight, when the difference in solar zenith angles increases, electron density values diverge. When both radars are in night conditions (solar zenith angle >99°) electron densities at the overlapping altitudes again become equal. We use the joint measurements to validate model computations of the ionospheric parameters f+, λ, αeff and their variations during solar proton events. These parameters are important characteristics of the lower ionosphere structure which cannot be determined by other methods.

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Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations: importance of lower ionospheric chemistry

10.5194/acp-2019-1133 ◽

2020 ◽

Author(s):

Niilo Kalakoski ◽

Pekka T. Verronen ◽

Annika Seppälä ◽

Monika E. Szeląg ◽

Antti Kero ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Lower Ionosphere ◽

Solar Proton ◽

Atmospheric Effects ◽

Ion Chemistry ◽

Global Models ◽

Superposed Epoch Analysis ◽

D Region ◽

Solar Proton Events

Abstract. Atmospheric effects of solar proton events (SPE) have been studied for decades, because their drastic impact can be used to test our understanding of upper stratospheric and mesospheric chemistry in the polar cap regions. For example, SPEs cause production of odd hydrogen and odd nitrogen, which leads to depletion of ozone in catalytic reactions, such that the effects are easily observed from satellites during the largest events. Until recently, the complexity of the ion chemistry in the lower ionosphere (i.e. in the D region) has restricted global models to simplified parameterizations of chemical impacts induced by energetic particle precipitation (EPP). Because of this restriction, global models have been unable to correctly reproduce some important effects, such as the increase of mesospheric HNO3 or the changes in chlorine species. Here we use simulations from the WACCM-D model, a variant of the Whole Atmosphere Community Climate Model, to study the statistical response of the atmosphere to the 66 largest SPEs that occurred in years 1989–2012. Our model includes a set of D-region ion chemistry, designed for a detailed representation of the atmospheric effects of SPEs and EPP in general. We use superposed epoch analysis to study changes in O3, HOx (OH + HO2), Clx (Cl + ClO), HNO3, NOx (NO + NO2) and H2O. Compared to the standard WACCM which uses an ion chemistry parameterization, WACCM-D produces a larger response in O3 and NOx, weaker response in HOx and introduces changes in HNO3 and Clx. These differences between WACCM and WACCM-D highlight the importance of including ion chemistry reactions in models used to study EPP.

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Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations: the importance of lower ionospheric chemistry

10.5194/egusphere-egu21-14579 ◽

2021 ◽

Author(s):

Niilo Kalakoski ◽

Pekka T. Verronen ◽

Annika Seppälä ◽

Monika E. Szeląg ◽

Antti Kero ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Lower Ionosphere ◽

Solar Proton ◽

Atmospheric Effects ◽

Ion Chemistry ◽

Global Models ◽

Superposed Epoch Analysis ◽

D Region ◽

Solar Proton Events

Atmospheric effects of solar proton events (SPEs) have been studied for decades, because their drastic impact can be used to test our understanding of upper stratospheric and mesospheric chemistry in the polar cap regions. For example, odd hydrogen and odd nitrogen are produced during SPEs, which leads to depletion of ozone in catalytic reactions, such that the effects are easily observed from satellites during the strongest events. Until recently, the complexity of the ion chemistry in the lower ionosphere (i.e., in the D region) has restricted global models to simplified parameterizations of chemical impacts induced by energetic particle precipitation (EPP). Because of this restriction, global models have been unable to correctly reproduce some important effects, such as the increase in mesospheric HNO3 or the changes in chlorine species. Here we use simulations from the WACCM-D model, a variant of the Whole Atmosphere Community Climate Model, to study the statistical response of the atmosphere to the 66 strongest SPEs which occurred in the years 1989&#8211;2012. Our model includes a set of D-region ion chemistry, designed for a detailed representation of the atmospheric effects of SPEs and EPP in general. We use superposed epoch analysis to study changes in O3, HOx (OH + HO2), Clx (Cl + ClO), HNO3, NOx (NO + NO2) and H2O. Compared to the standard WACCM which uses an ion chemistry parameterization, WACCM-D produces a larger response in O3 and NOx and a weaker response in HOx and introduces changes in HNO3 and Clx. These differences between WACCM and WACCM-D highlight the importance of including ion chemistry reactions in models used to study EPP.&#160;

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Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations: the importance of lower ionospheric chemistry

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-8923-2020 ◽

2020 ◽

Vol 20 (14) ◽

pp. 8923-8938 ◽

Cited By ~ 2

Author(s):

Niilo Kalakoski ◽

Pekka T. Verronen ◽

Annika Seppälä ◽

Monika E. Szeląg ◽

Antti Kero ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Lower Ionosphere ◽

Solar Proton ◽

Atmospheric Effects ◽

Ion Chemistry ◽

Global Models ◽

Superposed Epoch Analysis ◽

D Region ◽

Solar Proton Events

Abstract. Atmospheric effects of solar proton events (SPEs) have been studied for decades, because their drastic impact can be used to test our understanding of upper stratospheric and mesospheric chemistry in the polar cap regions. For example, odd hydrogen and odd nitrogen are produced during SPEs, which leads to depletion of ozone in catalytic reactions, such that the effects are easily observed from satellites during the strongest events. Until recently, the complexity of the ion chemistry in the lower ionosphere (i.e., in the D region) has restricted global models to simplified parameterizations of chemical impacts induced by energetic particle precipitation (EPP). Because of this restriction, global models have been unable to correctly reproduce some important effects, such as the increase in mesospheric HNO3 or the changes in chlorine species. Here we use simulations from the WACCM-D model, a variant of the Whole Atmosphere Community Climate Model, to study the statistical response of the atmosphere to the 66 strongest SPEs which occurred in the years 1989–2012. Our model includes a set of D-region ion chemistry, designed for a detailed representation of the atmospheric effects of SPEs and EPP in general. We use superposed epoch analysis to study changes in O3, HOx (OH + HO2), Clx (Cl + ClO), HNO3, NOx (NO + NO2) and H2O. Compared to the standard WACCM which uses an ion chemistry parameterization, WACCM-D produces a larger response in O3 and NOx and a weaker response in HOx and introduces changes in HNO3 and Clx. These differences between WACCM and WACCM-D highlight the importance of including ion chemistry reactions in models used to study EPP.

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The high latitude D-region and mesosphere revealed by the EISCAT incoherent scatter radars during solar proton events

Advances in Space Research ◽

10.1016/0273-1177(95)00844-5 ◽

1996 ◽

Vol 18 (3) ◽

pp. 83-92 ◽

Cited By ~ 1

Author(s):

P.N. Collis

Keyword(s):

High Latitude ◽

Solar Proton ◽

Incoherent Scatter ◽

Incoherent Scatter Radars ◽

D Region ◽

Solar Proton Events

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Night-time d-region electron density variations observed in the South Atlantic geomagnetic anomaly in association with solar-proton events

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/0021-9169(94)00068-y ◽

1995 ◽

Vol 57 (8) ◽

pp. 899-904 ◽

Cited By ~ 2

Author(s):

A. Mendes da Costa ◽

L. Rizzo Piazza

Keyword(s):

Electron Density ◽

Solar Proton ◽

South Atlantic ◽

The South ◽

Night Time ◽

D Region ◽

Solar Proton Events ◽

Geomagnetic Anomaly

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Reaction of the high-latitude lower ionosphere to solar proton events from observations in the ELF range

Geomagnetism and Aeronomy ◽

10.1134/s0016793217010078 ◽

2017 ◽

Vol 57 (1) ◽

pp. 51-57 ◽

Cited By ~ 3

Author(s):

O. M. Lebed’ ◽

A. V. Larchenko ◽

S. V. Pil’gaev ◽

Yu. V. Fedorenko

Keyword(s):

High Latitude ◽

Lower Ionosphere ◽

Solar Proton ◽

Solar Proton Events

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Indirect determination of the energy spectra of particles precipitated in the lower ionosphere associated with solar proton events

Geofísica Internacional ◽

10.22201/igeof.00167169p.2000.39.1.290 ◽

2000 ◽

Vol 39 (1) ◽

pp. 13-19

Author(s):

Aracy Mendes da Costa

Keyword(s):

Lower Ionosphere ◽

Solar Proton ◽

Energy Spectra ◽

Indirect Determination ◽

Solar Proton Events

Los perfiles de densidad electrónica medidos previamente usando la fase y la amplitud de radio señales VLF que se reciben durante los eventos más intensos de protones solares (SPE), junto con el espectro asociado de energías de protones y electrones, los cuales se miden simultáneamente por satélite, nos permiten calcular la razón de producción q(h) de los pares electrón-ion, para las regiones sub-Antártica y Sur Atlántica de la Anomalía Geomagnética (SAGA). Se usaron gráficas de q(h) junto con los perfiles verticales de la densidad electrónica previamente determinados, para calcular el coeficiente efectivo de recombinación Ïˆ(h) para la región SAGA. Asumiendo que los procesos químicos que se llevan a cabo en la baja ionosfera producidos por el impacto de los constituyentes atmosféricos neutrales son básicamente los mismos, se estiman indirectamente los espectros de las partículas energéticas responsables de la ionización detectada con cierto retraso en la región SAGA. Los parámetros que se obtienen coinciden con los resultados presentados por otros muchos autores para el hemisferio norte, además los espectros deducidos están dentro de los límites impuestos por la rigidez magnética y la profundidad de penetración de las partículas incidentes. Los datos experimentales que se presentan en este trabajo corresponden a las señales en VLF transmitidas desde Australia (NWC-22.3 kHz) y Î©-Trinidad (13.6 kHz) y que se recibieron en Atibaia y Curitiba respectivamente, ambas en Brasil, durante el evento de partículas de agosto 4-7, 1972.

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