formation of local atmospheric electric field under...

FORMATION OF LOCAL ATMOSPHERIC ELECTRIC FIELD UNDER THE INFLUENCE OF IONIZATION FACTORS

E.A. Ponomarev1, N.V. Cherneva2, P.P. Firstov3 1Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia; 2Institute of Cosmophysical

Research and Radio Wave Propagation FEB RAS, Kamchatka, 684034, Russia, e-mail: [email protected] ; 3Institute of Volcanology and Seismology FEB RAS, Russia,

Petropavlovsk-Kamchatskiy

Abstract. The influence of different ionization factors on the formation of local atmospheric electric field (AEF) in the near-ground layer is considered in the present work. Estimations of change of AEF strength (EZ) due to conductivity variations under the influence of radon and cosmic ray intensity are presented. It is shown that atmospheric conductivity changes due to ionization under the influence of radon emanations and it is determined by excalation and turbulent diffusion of the near-ground layer, while cosmic ray intensity affects to the conductivity of the near-ground layer under the influence of change of ion recombination state. The decrease of atmospheric conductivity, determined by cosmic ray flux, decreases EZ whereas the decrease of radon sink leads to EZ increase. The valuation of influence of light conditions on AEF value due to the change of relative concentration of heavy and light ions under the influence of photodetachment and photoattachment processes is given. This process may, evidently, explain the morning maximum for the days with fair weather conditions in diurnal EZ variation. It is shown, that the effect of “spread current” potential from auroral electrojet region to mid latitudes during geomagnetic disturbances may contribute AEF variations is about 5%.

Introduction The high sensitivity of an electrical field of an atmosphere (EFA) to the most various natural factors has determined low selectivity of monitoring systems based on the use of EFA. There was a problem of research and classification of the factors forming an electrical field of an atmosphere in the observation point. Today it is known, at a qualitative level, that EFA is determined, basically, by radon concentration in near ground layer, intensity of cosmic rays, light exposure of an atmosphere, managing photoionization processes, influencing on balance of heavy and easy ions in an atmosphere, variations of the electrosphere potential. The generalized scheme of cause-consequence relations EFA under influence of some natural processes is given in Fig.1.

Fig.1. The scheme of processes of formation of an electrical field of an atmosphere in the presence of the factors

determining its size in near ground layer. The letters R22 and R21 mark areas of modulation of atmosphere resistance under action of the ionizator qR (radon) and qC (cosmic rays). It is supposed that the action of stick and unstuck processes are both in area R22, and in area R21, that is symbolized by an index n in a circle. The situation of areas R22 and R21 at heights is shown on the insertion h22 и h21 (not in scale).

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)

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The features of seasonal course EFA. On the basis of the data received at observatory “Paratunka” during 1998-2008 at a qualitative level the connection Ez of EFA with a flow radon to near ground layer of the atmosphere is shown. In the area of observatory “Paratunka negative daily average T is keeping about 5 months from November to May. These months are conditionally named "winter". In winter months the sharp fluctuations T up to 15oC, caused by arrival of warm cyclones, with trajectories taking place through water area of Pacific Ocean, are observed which are accompanied by fluctuations P with amplitude up to 25 gPa. During negative daily average temperatures (November - April) the arrival of cyclones from southern directions is accompanied by significant reduction Ez EFA at the expense of increase of a flow Rn under influence of strong fall of atmospheric pressure and sharp warming up on 10-15o. Tropical cyclones, which come on Kamchatka from a southwest direction, influence on all parameters of the bottom atmosphere [3]. As the example the cyclonic activity was considered in details, when two cyclones has approached to peninsula Kamchatka at once, the trajectories are shown in Fig. 2-a.

Fig. 2. Trajectory of the cyclones which have arisen in water area of Pacific Ocean 8 and January 9, 2002 - (a);

azimuth distribution of lighting discharges and epicenters of cyclones - (b); distance from epicenters of cyclones up to observatory “Paratunka”" - (c). Dynamics of an atmospheref parameters during passage of a southern cyclone: P - atmospheric pressure, T - temperature of air - (d); quantity of atmospherics at one o'clock (e); intensity EFA, instant and time-averaged meanings - (f); volumetric activity Rn, 1-point PRT, 2 –point GLL (F).

Azimuth distribution of atmospherics is shown by points in Fig. 2-b from January 8 to January 16, 2002 according to the data VLF direction finder. The situation of cyclone epicenters are marked by the rhombuses in fig 2-a. It is visible in comparison of Fig. 2-b and 2-c, that at the approach of a cyclone to the place of registration the quantity of atmospherics is increased. In the period from January 10 to January 12 the cyclone epicenter has approached up to 50 kms to the observatory “Paratunka”. In Fig. 2-d where dynamics of meteorological sizes is shown, the cyclones have brought significant quantity of heat. Atmospheric pressure of January 10, since 14 hours sharply began to fall, and


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temperature of air – to grow. The difference of pressure has made 30 gPa, and temperature (-15o-2 o) 14 oC , and precipitations as sleet have begun to drop out at the end of January 12 , that has resulted to strong disturbances both VLF - radiation (Fig. 2 -e), and Ez EFA (Fig. 2-f). Dynamics of ground Rn on two points, located near the observatory, is shown in Fig. 2-g. It is visible, that VA Rn in the zone of aeration at both points has increased synchronously in 4 times from 2 up to 8 kBk/m3. Such powerful increase of the flow Rn to an atmosphere is caused by "exhausting" effect of fall of pressure and increase of permeability of mountain breeds under action of temperature increase. In one’s turn the increased flow radon to the near ground layer, obviously, has resulted to the increase of its ionization and conductivity, that has resulted to the fall of Ez EFA. The coefficient of correlation between Rn and Ez has made -0.43, at 0.3 for 95 % for a level of confidence. There is the interaction of geogas with atmospheric air on border of porous environment and atmosphere. Air enters to pores at increase of atmospheric pressure and "compresses " the geogas, and at reduction – air and a part of geogas leaves from pores. So on the average, "the evacuation" of geogas to an atmosphere occurs for the period of change of atmospheric pressure [4, 5]. The connection between a seasonal dependence Ez, capacity of a snow cover and temperature at observatory “Paratunka” was analysed. Decadely average data of snow cover heights and temperatures of air were used. It is visible in Fig. 3, that the maximum of capacity of snow cover falls at the branch of recession of the seasonal course Ez with maximal coefficient of correlation rmax = 0.73 (at r = 0.49, for 95 % of a level of confidence) at shift per 50 day. While the minimum of a seasonal course of temperature almost coincides with a maximum Ez, at shift per 10 day rmax = - 0.67 (r = - 0.42 for 95 % of a level of confidence). It specifies, that the seasonal courses Ez and temperature of air are in antiphase, that, apparently, is connected with the increase of a flow Rn to an atmosphere in summer at the expense of increase of permeability of the top ground layer, and the snow cover influences little on dynamics Ez.

Fig.3. Height of a snow cover and seasonal course of intensity EFA and temperature of air: 1-intensity EFA,

2-height of snow cover, 3-temperature of air.

Influence of Forbush-reduction on EFA The influence of Forbush-reduction on dynamics Ez EFA is shown for days with conditions of fair weather (CGW). The reduction galactic cosmic rays (GCR) on 3-10% results in essential reduction Ez EFA on 20 - 80 %. High-altitude distribution of the source of ionization, connected with cosmic rays, is more stable, than distribution ionizator in near ground layer. Nevertheless, there is one type of the variation of intensity and spectrum of cosmic rays, which essentially has an effect for the value of near ground EFA. It is so-called Forbush - effect. As shown in Fig. 7, the decrease of Ez magnitude is synchronously with Forbush-reduction of GCR and is sometimes shown convincingly enough.


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21 cases were chosen for the analysis. Unfortunately, practically in all cases time CGW on Kamchatka has appeared less than time of restoration Ez, which, as was shown on the data of observatory "Nagycenk", makes 5 days [2, 6]. Most typical curve, showing Forbush-reduction of intensity GCR simultaneously with reduction of Ez, are shown in Fig. 4-a. The results of data analysis show, that the reduction of Ez begins practically simultaneously with the beginning of Forbush-reduction, the delay of a variation of the signal Ez concerning Forbush-reduction does not exceed two hours. The speeds of reduction of sizes of intensity of a flow GCR and EFA practically coincide.

Fig.4. Most typical curve Forbush- reduction GCR and variation Ez, registered on observatory

“Paratunka”- (a); connection between Forbush-reduction in GCR and reduction Ez on the observatory “Paratunka” data (b).

For 18 cases, when the reduction galactic cosmic rays and Ez were fixed very precisely, the functional connection Ez(%) =f (N, %) was investigated. The dependence y=9.64x−0.72 (Fig. 4 b) was received, from which it is visible, that the reduction Ez on 3-10% results in essential reduction Ez EFA on 20 -80 %. The features of daily course EFA In view of the geographical situation of the peninsula Kamchatka the feature of daily course Ez EFA is maximum at 18-20 hours, which is formed under the action both UT - variation, and sun-rise. It is necessary to note, that the zone time of observatory “Paratunka” outstrips time UT at 12 hours and, thus, maximum of Ez meanings during the greater period of year is to morning hours coinciding with sun-rise. The attempt of allocation of a UT-variation on observatory “Paratunka" was made in report [1]. The found out maximum of meanings Ez had on 19 - 20 hours UT, that was connected with UT-variations. However it became obvious at detailed elaboration, that the maximum in daily variations changes from 18 to 21 hours UT seasonally, that, apparently, specifies influence both UT - variations, and terminator on a maximum of a daily course for observatory “Paratunka". The quiet days were chosen with the purpose of the division influence of the effect UT - variation and morning terminator, into a daily course Ez for the period 1998 - 2006, when there were no sharp fluctuations. The general number of the chosen days were 203 days: March - 48, April - 46, May - 35, June -42, July - 32. Curves were constructed by the method of imposing of epoch, which were normalized on the maximal meaning, and time of the sun-rise (on the data


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"Kamchatka Hydrometer Service") was chosen as a zero point. The root-mean-square deviation did not surpass 14 %. As it is visible in Fig. 5 and, with some portion of conditionality, it is possible to allocate two maxima. In March they almost merge in one with relative amplitude 40 %, and in June – July they form two maxima separated on 1.5 hour and amplitude ~ 20 %. The average course Ez at the moment of the sun-rise, received by a method of imposing of epoch in 203 cases of fair weather, chosen for spring-summer months 2004 and 2005, is shown in Fig. 5 b. As the beginning of epoch the sun-rise hour is chosen. It is visible, that in a two-hour interval after the beginning of epoch the smooth maximum as the size some percents is observed. The experimental confirmations of influence nonequipotential of the electrosphere on a variations Ez are received.

Fig.5. Allocation morning terminator on a background of UT - variation in EFA on observatory

“Paratunka " - (à); allocation of sun-rise effect in EFA by a method of imposing of epoch The example of allocation of "ionospheric" variation of the electrical field of an atmosphere by a method of imposing of epoch for 37 geomagnetic bays is given in Fig. 5 c. The beginning of a bay is taken as zero epoch. The cases about local midnight are selected. At average size of an electrical field ~ 120-140 v/m it is about 5 % - the value leaving for statistical errors of a method and, it is basically detected. Conclusions: 1. On the basis of long-term numbers of the data, the seasonal dependence Ez EFA from a flow radon into near ground layer of the atmosphere is shown. During negative daily average temperatures (November - April) the arrival of cyclones from southern directions is accompanied by significant reduction Ez EFA at the expense of increase of a flow Rn under influence of fall of atmospheric pressure and sharp getting warmer on 10-15o. 2. In view of the geographical situation of a peninsula Kamchatka the feature of daily course Ez EFA is maximum at 18-20 hours, which is formed under action both UT - variation, and sun-rise effect (morning terminator).


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3. The influence of Forbush-reduction on dynamics Ez EFA is shown for days with conditions of fair weather. The reduction of GCR on 3-10% results in essential reduction of Ez EFA on 20 - 80 %. References: 1. Buzevich A.V., Cherneva N. V., Ponomarev E.A. Observations of many years and morphology

of the variations of electrical field Ez in Kamchatka. Coll. of reports III int. conf. ”Solar-Terr. Relations and Electromagnetic Precursors”. P-Kamchatsky. 2004. P.155-160.

2. Cherneva N. V., Kuznetsov V. V. Forbush-reduction and effects of terminator in atmospheric electrical field of Kamchatka. Int. Baikal school on fundamental physics “Astrophysics and Physics of near Earth space environment”. Irkutsk. 2005. Pt I. P.37-40.

3. Kuznetsov V. V., Cherneva N. V., Druzhin G. I. Influence of Cyclones on the Atmospheric Electric Field of Kamchatka. ISSN 1028-334X, Doklady Earth Sciences. 2007. Vol. 412, №. 1. P. 147–150.

4. Firstov P.P., Cherneva N. V., Ponomarev E.A., Buzevich A.V. Under ground radon and intensity of electrical field of atmosphere in the area of Petropavlovsk-Kamchatsky. Vestnik KRAUNSCH. Science of Earth. 2006. №1. P.102-109.

5. Firstov P. P., Ponomarev E. A., Cherneva N. V., Buzevich A. V. and Malysheva O. P. On the Effects of Air Pressure Variations on Radon Exhalation into the Atmosphere. Journal of Volcanology and Seismology. 2007. V.1, № 6. P. 397.

6. Märcz F. Short-term changes in atmospheric electricity associated with Forbush decreases. J. Atm. Solar-Terr. Physics. 1997. V. 59. N. 9. P. 975-982.


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