Research On The Basic Features Of The Geoelectric Field Variation And The Physical Explanation

Earth electric field (geoelectric field for short) and variational geomagnetic field are two correlative geophysical fields in physical essence. The study of geoelectric field variation is an important way to understand and realize the inner and external environment of earth and important to the development of national economic construction , national defence, aviation, spaceflight and communication sciences and seismic scientific research..Limit to the problem of the long-term stability of electrode, however, the study of geoelectric field in the world is less extensive and in-depth than that of variational geomagnetic field. The observation and study of geoelectric field are focus on geophysical detection and geologic disaster forecast and alarm, such as seismic and volcano since long term in domestic and abroad.In recent years, with the development of geoelectric field observation technology, geoelectric field long-term fix spot observation is developed in succession. From the term of"the ninth five years plan", the large-scale, digital and fixed observation of geoelectric field has been developed in mainland of China, and abundant data has been accumulated, which make a new foreground on geoelectric field time and space variations study of earth electromagnetic environment.We process and analyze the minute-value data of 12,194 days from 21 geoelectric field observatories and that of 2677 days from 5 geomagnetic observatories in the range of E 98 13' ~ 126 35' and N 30 30 ' ~ 44 52'of the China mainland, then study the geoelectric field quiet day variations, disturbed day variations, seasonal variations and its spectrum characteristics, wide regional nature and locality in detail. Thus, we have the following understandings and conclusions:1. The large-scale, digital and fixed observation of geoelectric field has been developed in recent year. The general quality of geoelectric field data is good and may be used in study of the earth's electromagnetic field and in other applications, but the observational technique of geoelectric field and the data quantity should be improved further.2. The pattern of the quiet day changes of geoelctric field is similar in a wide region and has not an obvious relation to geographic longitude and latitude, but there are some differences of day changes patterns between different stations. The time which the wave crest and wave hollow of the changes appear in is later at the observatory in the west China than at that in the east, and their time difference is accordant with that of local Beijing time, but at times that is obvious between the observatories near same longitude (but sometimes the arriving times are different in same longitude). The periods of the changes are respectively 24 ? h, 12 ? hand 8 ? h as well as 6 ? h, 4 ? hand tens minutes to several minutes, among which the semidiurnal waves of the 12 ? hperiod is the strongest part that appears in a wide region. The amplitude of the changes is basically in the range from several mV/Km to 17.7mV/Km that will clearly decrease with the increase of the latitude and obviously shows the local nature. The seasonal variation of the amplitude is in accordance with the Loyd season in astronomy.3. The quiet day changes of both geoelectric field and geomagnetic field could originate from same a field source which comes from the ionospheric disturbances caused by the earth's magnetospheric space compressed by the solar wind and the charged particles. The geoelectric storm and the quick changes of geoelctric field short term variation will occur simultaneously in a wide region, with a very quick abrupt and a great amplitude, and they could be caused by the current source of the earth's outer space.