O.I. Shumilov

Arctic ozone abundance and solar proton events

In this study it is documented for the first time that the atmospheric ozone column density is decreased during solar proton events, GLEs (Ground Level Events), events with protons having energy exceeding 50 MeV and penetrating down to the ground. The ozone decrease was significant at the polar cap stations, Longyearbyen and Barentsburg at 78° N, whereas it was not detectable at the auroral zone stations Murmansk (69° N) and Tromso (70° N). The duration of the depletion was limited to the days of the proton precipitation, and the depletion may be explained by the ability of energetic protons to produce nitric and hydrogen oxides in the stratosphere and their catalytic reactions with ozone. Similar events are identified in the Antarctic.

POLAR STORMS AND DEVELOPMENT OF THE DR CURRENTS.

Abstract The connection of the intensity of polar disturbances with the value of the DR-variation is considered. It is shown that at the moments of DR-field maxima the intensity of the field DR is proportional to the total energy of the particles entering the upper atmosphere of the Earth. It is suggested that the acceleration of the auroral particles and filling up the DR belt are due to the same process.

Ozone “miniholes” initiated by energetic solar protons

Abstract In this study, it is shown that during four Solar Proton Events (SPE), mostly of the Ground Level Event (GLE) type (May 1990, September and October 1989, and March 1989), inside the polar cap in the Arctic (or the Antarctic) short-term depletions were observed (up to 20%) in the ozone total content. These depletions or so-called ozone “miniholes” seem to be caused by energetic solar protons with energies of 150–300 MeV. For May 1990, the gas phase photochemical model includes only 1% ozone depletion compared with 18% observed at Barentsburg (Svalbard), and for none of the other events can homogeneous processes explain the observed depletion. The problem seems to be solved considering heterogeneous reactions in the presence of increased amounts of aerosol particles in the stratosphere which may be triggered by penetrating solar protons, or through an additional decrease of temperature, or through an increase of volume electric charge in the stratosphere (or even troposphere).

Solar cosmic ray effects in atmospheric chemistry evidenced from ground-based measurements

Abstract Ground-based measurements of nitrogen dioxide (N02) total content and photochemical modeling have been used to investigate the response of high-latitude atmosphere to solar proton events of Ground Level Event (GLE) type. Measurements of NO 2 were made at Murmansk, Kola Peninsula (corrected geomagnetic latitude: 64.8°) during and after GLE of 2 May 1998. Nitrogen dioxide was measured by zenith viewing spectrophotometer in wavelength range between 435 and 450 nm. An increase (about of 20%) in total column of N02 has been detected after 2 May 1998 GLE by this facility. Model calculations based on gas phase photochemical theory quantitatively agree with observations. These results demonstrate that information obtained from ground-based measurements is usable to study the atmospheric effects of high-energy solar protons in addition to satellite data.

Simultaneous occurrence of IPDP and auroral absorption as indication of joint westward drift of protons and electrons

Abstract The dynamics of the intervals of pulsation of diminishing periods (IPDP) generation region and that of the auroral absorption (AA) are compared. It is known that IPDP is the manifestation of the ion-cyclotron instability due to precipitation and drift of protons and AA is the result of electron precipitation. The westward movement in space and time of the AA and IPDP generation region was revealed. This is the first experimental confirmation of the joint westward drift of the electron and proton in the form of neutral clouds in the magnetosphere during an auroral substorm.

Detection of infrasound from the Vitim bolide on September 24, 2002

An infrasonic signal from an atmospheric bolide explosion was detected on September 24, 2002 near the Vitim river, Irkutsk region (57.9 N, 112.9 E). The signal was detected by three spatially separated microbarographs of the Polar Geophysical Institute (PGI), Kola Science Center, Russian Academy of Sciences, Apatity (67.6 N, 33 E) at a distance of 4000 km from the source. The acoustic gravity signal from a falling meteorite at high latitudes was detected at such a distance for the first time in Russia.

Software for dendrochronological measurements

The tree-ring measurement tool (TREMET) program has been developed for measuring the width of tree growth rings by images with any resolution recorded by capture devices (flatbed scanners, digital cameras, etc.). The program can be used to obtain dendrochronological information from various samples (cores, saw cuts), particularly from difficult-to-treat samples. The TREMET program has been used to create a 676-year tree-ring chronology from juniper samples, including relic plants gathered on the Cola Peninsula. This program is the longest juniper chronology in the northwest region of Russia. Using the TREMET program, the longest tree-ring chronologies have been obtained for pine of the Khibiny Mountains (448 years) and the Cola Peninsula (561 years).

Ozone variations in the Scandinavian sector of the Arctic during the AASE Campaign and 1989

The Airborne Arctic Stratospheric Expedition (AASE) carried out measurements from January 3 to February 15, 1989. Enhanced levels of chlorine compounds were found in the Arctic stratosphere, and on two single flights ozone decrease of 17% were measured, interpreted as essential features of the Arctic stratosphere, caused by a combined effect of enhanced amounts of chlorine compounds and presence of polar stratospheric clouds. Related model calculations also indicate extended ozone depletion maximizing in late March 1989 and amount to 5–8% in column at 70° N. Ground-based ozone measurements, however, show that the most characteristic features during this period are temporal variations and a strong enhancement of ozone, probably due to an extended stratospheric warming. From these measurements it is hard to see any effect of an eventual enhanced burden of stratospheric chlorine, which might show up as an extended and long-lasting decrease of stratospheric ozone, but its eventual existence is masked by the temporal variations.

Quasi-drift effects of high-energy solar cosmic rays in the magnetosphere

The structure of high-energy solar proton penetration zones in the polar and subpolar regions using data from riometers, transpolar satellite DMSP-F6, and neutron monitors during an extremely anisotropic solar proton event on February 16, 1984, has been studied. Particular emphasis was placed upon interpretation of the solar proton intensity maximum located at the auroral and nearby latitudes. Precipitation of quasi-trapped particles drifting along the latitudinal direction from the entry site of the anisotropic flux at the dawnside of the magnetosphere is discussed as a cause of this maximum.

The ionospheric effects in D-layer and solar proton precipitation zones during the 16 February 1984 event

Abstract The results of the geophysical and VLF (10–16 kHz) radio propagation measurements on the net of observatories during the solar proton event on 16 February 1984 are analysed. It is shown that the abnormal ionization region caused by solar protons consisted of two parts. One of them was the direct access zone in the middle and morning side of the polar cap, the other was the precipitation region of the quasi-trapped particles in the mid-day and evening sectors of the auroral zone. The probable profiles of the lower ionosphere electron density are determined from the VLF and satellite data of the energetic spectra at the maximum penetration. It is shown that the effective electron concentration at the height ∼45 km was close to ∼10 3 cm −3 .