Solar activity and space weather changes

Abstract

ABSTRACT Geomagnetic storms have a good correlation with solar activity and solar radiation variability. Many proton events and Geomagnetic storms have occurred during solar cycles21, 22, and 23. The solar activities during the last three cycles, gave us a good indication of the climatic change and its behavior during the 21 st century. High energetic eruptive flares were recorded during the declin e phase of the last three solar cycles. The a ppearances of the second peak on the decline phase of solar cycles have been detected. Halloween storms during Nov. 2003 and its effects on the storms have been studied analytically. The data of amplitude and phase of most common indicators of activities during solar cycle 23 have been analyzed. 1. INTRODUCTION One of the most important solar phenomena is the evidence of solar activity, which has been found to be periodic with an around 11year cycle. Th e occurrence of the cycle is a magnetic phenomenon, related to the dynamo effect, which generates the magnetic field of the sun ( Zeldovich, et al 19 83). The energetic solar events , which associated with peak and decline phase of the solar cycles, can be affected on earth's atmosphere, satellites, and on humankind activity. The solar cycle is important because it determines the long term variation of regions such as the earth’s ionosphere, a layer of charged particles between 100 and 600 km above the surface of th e earth. This layer is important because of its effect on radio signals, either reflecting high frequency signals or retarding those above this frequency range. The solar cycle also underpins the occurrence of short term di sturbances to the earth-sun region. Thes e arise in association with spectacular events on the sun such as solar flares and coronal mass ejection’s and propagate to the earth as changes in the solar wind, an outflow of charged particles from the sun which envelopes the earth. Disturbances disrupt the ionosphere causing rapid variations in its properties and are most obviously seen in the rapid variations in the magnetic field of the earth, events that are known as geomagnetic storms. A storm is a temporary disturbance of the Eart h's magnetosphere caused by a disturbance in space weather. Associated with solar coronal mass ejectio ns (CME), coronal holes, or solar fl ares, a storm is caused by a solar wind shock wave that typically strikes the Earth's magne tic field 24 to 36 hours after the event. This only happens if the shock wave travels in a direction toward Earth. The solar wind pressure on the magnetosphere will increase or decrease depending on the Sun's activity. These solar wind pressure changes modify the electric currents in the ionosphere. Magnetic storms usually last 24 to 48 hours, but some may last for many days. The energetic solar events, especially during the decline of so lar cycles, can affects on eart h's atmosphere, satellites, and on humankind activity. Recently, the observations has revealed the solar energetic particles (SEPs) and coronal mass ejections (CMEs) with different origins, based on magnetic changes of the active region which produced the SEPs, and based on the abundances, ionization states and time production of the particles as well as the longitude distribution associations of the events see for example: Reames, D.V. (1994) and Ream es, D.V (1995). These events (SEPs and CMEs) led to severe effects on the Earth, such as power blackouts, disruption of communications, and damage of satellites. It is well known that solar activity exhibits an 11-year periodicity, and the more dramatic activities usually occur in the maximum of the cycle. The complicated dynamics of magnetic fi elds, plays a key role in the solar activities, see Parker (2001). The peak of the Solar cycle 21 wa s at 1979 but high energetic Solar flares, or secondary peaks, occurred at the declining phase in 1981, 1982, and 1984 before the solar activity minimum in 1986. Also, the peak of the solar cycle 22 was at 1989 but high energetic solar flares occurred at the declining phase in 1991, 1992, and 1994, before the solar