E. A. Kasatkina

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.

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.

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).

Features of amplitude and Doppler frequency variation of ELF/VLF waves generated by “beat-wave” HF heating at high latitudes

Observations of extremely low frequency (ELF, 3–3000 Hz) radio waves generated by a “beat-wave” (BW) high frequency (~ 4.04–4.9 MHz) ionospheric heating are presented. ELF waves were registered with the ELF receiver located at Lovozero (68°N, 35°E), 660 km east from the European Incoherent Scatter Tromso heating facility (69.6°N, 19.2°E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

Consequences of powerful volcanic eruptions according to dendrochronological data

For the first time we identify the peculiarities of the effect of the most powerful (VEI > 5) volcanic eruptions on the regional climate of the Murmansk region on the basis of Kola Peninsula dendrochronological data for a period of more than 560 years. The analysis was based on the tree-ring chronology covering the period from 1445 to 2005. This chronology was derived from Pinus sylvestris samples collected near the northern tree line at Loparskaya station (68°37′ N; 33°14′ E). The data were processed using modern techniques adopted in dendrochronology (cross dating and standardization). We reveal a significant decrease in the radial tree-ring growth over 8 years (on average) after the eruptions; then its value is restored to the normal level. This finding will help evaluate the response of the regional climate system to external climate forcings in this economically important region for Russia.

One more puzzle of the Tunguska catastrophe

Using the results of the dendrochronological analysis (68 tree-ring chronologies), it has been shown that the increase in the annual growth of trees after the Tunguska bolide explosion on June 30, 1908, is observed at a large distance (more than 1500 km) from the explosion site (61° N, 102° E) and covers a huge area of about 2 × 106 km2 (60°–75° N, 80°–110° E). The anomalous growth of the trees was previously reported only for the direct-destruction area (about 2000 km2). A similar result was obtained when analyzing changes in the annual growth at the time of the Chulym bolide explosion on February 26, 1984 (57.7° N, 85.1° E). A possible interpretation of the observed phenomenon is given. The results open new opportunities for using the dendrochronological method to solve the problems of asteroid-comet danger.

Effects in the Geomagnetic Field and Absorption of Cosmic Radio Emission Caused by the Negative Pressure Discontinuity of the Solar Wind: Analysis of a Particular Event

An abrupt decrease in the solar wind pressure and its effect on the magnetosphere and ionosphere during the event occurring on April 4, 1971, are studied. This event differs fundamentally from a typical sudden commencement (SC) of a geomagnetic storm or from a positive sudden impulse (SI+) and is determined as a negative sudden impulse (SI–). The geomagnetic variations at different latitudes and the cosmic radio emission in the auroral zone are analyzed. From the data of low-latitude geomagnetic observatories, several subsequent negative impulses observed with a periodicity of ~45 min were found. At the same time, a sudden decrease in the absorption of cosmic radio emission in the auroral zone was revealed. Possible physical explanations of the observed changes are discussed.

Urban Heat Island Investigations in Arctic Cities of Northwestern Russia

Urban microclimate peculiarities in two Arctic cities in northwestern Russia—Kirovsk (67.62°N, 33.67°E) and Apatity (67.57°N, 33.38°E)—were investigated by using mobile temperature records. The experiment was carried out in and around Apatity and Kirovsk in February 2014 and December 2016. The DS18B20 digital thermometer was installed on the roof of a car (height: approximately 1.2 m) to measure and record temperature variations automatically. In addition to the digital thermometer, the car was also equipped with an onboard global positioning system, allowing every temperature measurement to be referenced with an altitude and a latitude/longitude position. The possibility of urban heat island formation in these polar cities, above the Arctic Circle, was studied. Our analysis indicated that on 11 February 2014, the temperature varied in accordance with the background environmental lapse rate (–0.0045°C m–1), and nearly corresponded to it (–0.0165°C m–1) on 12 February 2014. On 6 December 2016, a strong local temperature inversion with a positive value of 0.032°C m–1 was detected, seemingly caused by the formation of a cold air pool in the valley near Kirovsk. It was found that the temperature variations within and outside these cities are strongly influenced by local topographic effects and the physical conditions of the atmospheric boundary layer.