Total ozone decrease in the Arctic after REP events

International audienceEight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10-14 kHz) monitored along the Aldra (Norway) - Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55-50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger than that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes

Physics of Auroral Phenomena

Abstract. The average frequency of the first mode Schumann resonance is ~7.8 Hz. The first mode presents in reality a triplet. If the Earth-ionosphere cavity were horizontally homogeneous the three frequencies would be equal. The day-night ionospheric asymmetry as well as the auroral ionization enhancement lead to the frequency splitting. The splitting is difficult to reveal because damping masks it. We calculate the splitting from the diurnal variation of the first mode Schumann frequency using a simple resonance field model. The total magnetic field of the resonance is supposed to consist of three axially symmetric fields, each of the fields oscillating with a constant frequency. The orthogonal axes of symmetry are fixed in the solar-geographic coordinate system. One of the axes is directed sunward. The other axis is close to the Earth rotation axis. The third axis is perpendicular to the two ones. The summary field has rather complex polarization. Its effective frequency being a combination of the triplet frequencies is a function of the solargeographic coordinates, i.e. the latitude and local time. There is no dependence on the universal time in the simple model. When an observatory rotates together with the Earth, it registers the effective frequency varying with the local time, the variation being different in the H (north-south) and D (east-west) components. Observations at Kola and Kamchatka peninsulas were utilized for calculations of the triplet frequencies. The following values have been obtained for five quiet spring days: 8.10, 7.84, and 7.75 Hz. The model calculations of diurnal variation of the effective frequency coincide very well with the observation results at the both observatories. One of predictions of our model is that the D component at the Earth equator has no diurnal variation

Total ozone decrease in the Arctic after REP events

Eight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10-14 kHz) monitored along the Aldra (Norway) - Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55-50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger than that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (polar meteorology

Changes of the first Schumann resonance frequency during relativistic solar proton precipitation in the 6 November 1997 event

The variations of the first mode of Schumann resonance are analyzed using data from Kola peninsula stations during the solar proton event of 6 November 1997. On this day the intensive flux of energetic protons on GOES-8 and the 10% increase of the count rate of the neutron monitor in Apatity between 1220 and 2000 UT were preceded by a solar X-ray burst at 1155 UT. This burst was accompanied by a simultaneous increase of the Schumann frequency by 3.5%, and the relativistic proton flux increase was accompanied by 1% frequency decrease. These effects are explained by changes of the height and dielectric permeability of the Earth-ionosphere cavity.Key words. Ionosphere (ionospheric disturbances; solar radiation and cosmic ray effects) · Radio science (ionospheric propagation