Bow shock. “Beyond that distance, the fields in the northern and southern tail lobes are nearly antiparallel and have an almost constant intensity of about 20 nT over a long range of distances from the Earth.” https://t.co/O218eVjrnc
Bow shock. “The effects of the strong dipole are not seen tailward of about 20 RE.” https://t.co/O218eVjrnc
Bow shock. “The low-density tail lobes in the nightside magnetotail connect magnetically to the high-latitude polar caps at one end and to the interplanetary field at the other end.” https://t.co/O218eVjrnc
“As the solar wind flow past the magnetosphere is both supersonic and super-Alfvénic, a bow shock is formed upstream of the magnetopause, and the flow is decelerated within the magnetosheath between the shock and the magnetopause.” https://t.co/O218eVjrnc
“The magnetotail extends far beyond lunar orbit at least a few hundred RE in the antisunward direction.” https://t.co/O218eVjrnc
“In the antisunward direction, the solar wind flow deforms the dipolar magnetic field to a cometary taillike shape where the magnetopause is on average about 30 RE from the Sun-Earth line, depending on the solar wind pressure.” https://t.co/O218eVB2eK
Mag field deformation “under strong solar wind driving the magnetopause can be pushed well inside the geostationary orbit.” https://t.co/O218eVjrnc
Mag field deformation. “Typical solar wind conditions give a standoff distance of the magnetopause at about 10 RE (Earth radius = 6370 km) upstream of the Earth.” https://t.co/O218eVjrnc
“The magnetospheric boundary, the magnetopause, forms at a location where the solar wind and magnetospheric plasmas and magnetic fields are in pressure balance.” https://t.co/O218eVjrnc
“The size of the magnetospheric cavity is determined by the magnetic pressure of the internal field on one hand, and on the solar wind dynamic pressure on the other.” https://t.co/O218eVjrnc
“The intrinsic geomagnetic field of the Earth has an intensity of about 50,000 nT in the polar regions and about 30,000 nT at the equator.” https://t.co/O218eVjrnc
“The types of space weather phenomena at the different planets depend critically...on the distance from the Sun determining the properties of the driving solar wind and IMF.” https://t.co/O218eVjrnc
“The types of space weather phenomena at the different planets depend critically...on the existence and characteristics of the planetary atmosphere and ionosphere.” https://t.co/O218eVjrnc
“The types of space weather phenomena at the different planets depend critically on the magnitude of the intrinsic magnetic field.” https://t.co/O218eVjrnc
“Mercury has a small intrinsic field but no atmosphere, there the solar wind interacts directly with the surface and exosphere.” https://t.co/O218eVjrnc
“On the other hand, the inner solar system, Earth-like planets Venus and Mars possess no intrinsic magnetic field, and the magnetosphere is then mostly formed by interaction of the atmosphere and ionosphere with the solar wind flow.” https://t.co/O218eVjrn
A magnetosphere. “In the terrestrial case, the interaction is dominated by the strong intrinsic quasidipolar magnetic field; this is also the case of the outer giant planets Jupiter, Saturn, Uranus and Neptune.” https://t.co/O218eVjrnc
“A magnetosphere is a cavity in the solar wind flow formed by the interaction of the solar wind and interplanetary magnetic field with the intrinsic magnetic field or ionized upper atmosphere of a planetary body.” https://t.co/O218eVjrnc
“Thus, solar irradiation, energetic particle fluxes from the Sun, and the solar wind with its multiple structures all drive geomagnetic activity and are thus potential sources for space weather events.” https://t.co/O218eVjrnc
“The particle precipitation leads to an enhancement of NO2 in the atmosphere, which in turn is a catalyst for ozone destruction. This way the solar activity also affects the long-term balance of the atmospheric chemistry.” https://t.co/O218eVjrnc
The sun. “As the energetic particles can penetrate to 20–40 km altitude (depending on their energy), they also affect the middle and upper atmospheric chemistry while colliding with the atmospheric constituents.” https://t.co/O218eVjrnc
Solar energetic particles. “If they become trapped in the inner magnetosphere dipolar field, they populate the van Allen belts, residing in the magnetosphere for extended periods.” https://t.co/O218eVjrnc
“Solar energetic particles affect the space environment in multiple ways. In the outer magnetosphere (especially near the geostationary region), their presence is a hazard for the satellite systems and instrumentation.” https://t.co/O218eVjrnc
“The irradiance exhibits both long-term (solar cycle) variations as well as shorter term changes related to active solar events, both of which can be monitored using the F10.7 radio flux as a proxy.” https://t.co/O218eVjrnc
Solar heat. “This most familiar form of the Sun’s influence on the Earth is a factor also for space weather: Increases of the solar irradiance cause heating of the upper atmosphere, which affects the drag experienced by low-Earth-orbiting satellites.” http
“In addition to the interaction with the solar wind, the Sun affects the Earth’s environment also through electromagnetic radiation that reaches the Earth much faster than the solar wind flow.” https://t.co/O218eVjrnc
“The ram pressure pulse associated with the shock compresses the dayside magnetopause, and the compression effects travel tailward at the solar wind speed causing strong auroral activity observable almost instantaneously all around the auroral oval.” https
“Interplanetary shocks when interacting with the Earth’s bow shock cause direct energy transfer into the magnetosphere.” https://t.co/O218eVjrnc
“CIRs, being associated with the coronal hole structure, also exhibit 27-day periodicity.” (CIR = corotating interaction regions). https://t.co/O218eVjrnc
“The CIRs seldom have fast shocks or continuous, strongly southward IMF Bz, and thus drive only moderate magnetospheric activity.” CIR = corotating interaction regions); (IMF= interplanetary magnetic field). https://t.co/O218eVjrnc
“When the high-speed solar wind emanating from the coronal holes runs into the slower solar wind, the interaction leads to a compression of the plasma and magnetic fields, forming corotating interaction regions (CIR).” https://t.co/O218eVjrnc
“During the declining phase of solar cycles, the coronal holes extend to low latitudes sometimes even reaching the ecliptic plane.” https://t.co/O218eVjrnc
“The electron fluxes maximize during the declining phase of the solar activity when the high-speed streams are most frequent, and minimize during solar minimum.” https://t.co/O218eVjrnc
“These periods are effective drivers of medium-level activity in the high-latitude magnetosphere and in the ring current. The high-speed streams are especially efficient in accelerating relativistic electron populations in the outer van Allen belt.” https:
“Such high-speed streams are often associated with strong Alfvénic fluctuations leading to strong fluctuations of the IMF Bz and solar wind velocity.” https://t.co/O218eVjrnc
“High-speed solar wind streams encountering the Earth most often originate from low-latitude coronal holes.” https://t.co/O218eVjrnc
ICME= Interplanetary coronal mass ejection. https://t.co/O218eVjrnc
“Similarly to ICMEs, any coherent solar wind structures including long-lasting, high-intensity southward interplanetary fields drive magnetic storm activity with its many signatures in the magnetosphere-ionosphere system.” https://t.co/O218eVjrnc
“As ICMEs are more frequent during solar maximum than during solar minimum, they contribute to the 11-year cycle in magnetospheric activity.” (ICME= Interplanetary coronal mass ejection). https://t.co/O218eVjrnc
“While the strongly southward field inside the ICME proper tends to drive high ring current activity, the more variable fields and densities in the sheath region drive strongest activity at the high-latitude auroral regions.” https://t.co/O218eVjrnc
ICME= Interplanetary coronal mass ejection. https://t.co/O218eVjrnc
“The coherent magnetic field structure, the strongly varying field and plasma density in the sheath region preceding the ICME proper, the fast solar wind speed, as well as the interplanetary shock itself are all effective drivers of geomagnetic activity.”
“Coronal mass ejections (CME) expel vast clouds of solar magnetic flux and plasma into interplanetary space. The interplanetary structure formed by the coronal mass ejection (ICME) propagates outward from the Sun, often at high velocity.” https://t.co/O218
“There is a clear signal in the geomagnetic records arising from the Russell-McPherron effect due to the varying orientation of the Earth’s rotation axis relative to the Sun-Earth line as the Earth rotates around the Sun.” https://t.co/O218eVjrnc
Geo-magnetic changes. “The solar activity shows no annual variation.” https://t.co/O218eVjrnc
Figure 1 illustrates the close relationship of the long-term solar activity (characterized by the monthly mean of the sunspot number) and the geomagnetic activity using the planetary magnetic Ap index as a proxy.” https://t.co/O218eVjrnc
Solar cycle. “The activity level is at minimum during solstices when the projection of the IMF to the Earth’s field is on average at minimum.” (IMF= interplanetary magnetic field). https://t.co/O218eVjrnc
During the equinoxes “the dipole is tilted along the Earth’s orbital track and the projection of the IMF to the geomagnetic field maximizes.” https://t.co/O218eVjrnc
“As the orientation of the dipole axis relative to the Sun-Earth line changes over the course of the year, the activity is largest during the equinoxes.” https://t.co/O218eVjrnc
“In the longer term, the solar activity varies with the well-known 11-year cycle, which introduces an 11-year activity cycle also to the geomagnetic records.” https://t.co/O218eVjrnc
“Coherent solar wind structures containing southward magnetic fields and high velocities are thus most efficient drivers of space weather events.” https://t.co/O218eVjrnc
Geomagnetic activity. “As the dipole is close to perpendicular to the ecliptic plane, it is primarily dependent on the southward component of the IMF.” (IMF= interplanetary magnetic field). https://t.co/O218eVjrnc
“Geomagnetic activity is primarily driven by magnetic reconnection between the IMF and the terrestrial magnetic field.” https://t.co/O218eVjrnc
“The average direction of the interplanetary magnetic field along the Parker spiral in the ecliptic plane is at an angle of about 45° from the radial direction.” https://t.co/O218eVjrnc
“On average, the solar wind at Earth orbit has mean density of about 4 cm−3, mean velocity of about 400 kms−1, and mean interplanetary magnetic field (IMF) magnitude of 5 nT.” https://t.co/O218eVjrnc
“From space weather point of view the key question is how to distinguish those solar events that are geoeffective from those that are not.” https://t.co/O218eVjrnc
“The Sun affects the Earth and its environs in a variety of ways and on many different timescales. Events on the Sun leading to large perturbations in the coupled magnetosphere-ionosphere system are called geoeffective.” https://t.co/O218eVjrnc
“Today’s challenge for space weather research is to (ii) to extend the physical understanding also to solar processes such that predictions can be made using solar observations to gain more lead time.” https://t.co/O218eVjrnc
“Today’s challenge for space weather research is to (i) learn to quantitatively predict the state of the magnetosphere and ionosphere from measured solar wind and interplanetary magnetic field conditions.” https://t.co/O218eVjrnc
“As our capability of predicting solar wind properties from solar observations alone is poor, we are at the moment limited to at best warnings 80 hours in advance and predictions at maximum 1 hour before the event starts.” https://t.co/O218eVjrnc
The solar wind “monitors at the first Lagrangian point (L1), 1.4 million km from the Earth, provide measurements of the incoming solar wind that reaches the outer edges of the magnetosphere within about 40 minutes to 1 hour of their detection.” https://t.c
“The solar wind travel time from the Sun to the Earth is of the order of 80 hours.” https://t.co/O218eVjrnc
“Energetic particles reach the Earth within only a few, maybe up to ∼20 min after their release from the solar surface or interplanetary shock front giving only a very short lead time after a warning can be given.” https://t.co/O218eVjrnc
Space weather ranges down to “even minutes and seconds (particle acceleration events, plasma instability growth times).” https://t.co/O218eVjrnc
Space weather: “ranging from solar cycle and longer (long-term solar activity variations) to 27 days (recurrent solar activity), days (magnetic storms), hours (magnetospheric substorms)...” https://t.co/O218eVB2eK
“The solar and magnetospheric processes pose several timescales.” https://t.co/O218eVjrnc
“The time scales interesting to studies of space weather processes are determined both by the intrinsic time scales of the processes themselves, but also on the lead time that predictions can be given.” https://t.co/O218eVjrnc
“The adverse conditions in the space environment can cause disruption of satellite operations, communications, navigation, and electric power distribution grids on ground, leading to a variety of societal and economic losses.” https://t.co/O218eVjrnc
Space weather “can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health.” https://t.co/O218eVjrnc
“The term “space weather” now refers to conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and thermosphere (upper parts of the atmosphere).” https://t.co/O218eVjrnc
“Many of the basic physics questions concerning the Sun-Earth connection remain open.” https://t.co/O218eVjrnc
“The modern space era with detailed in-situ and remote sensing measurements in and from space have resolved many issues concerning the behavior of the Sun, the solar wind, and the terrestrial space environment.” https://t.co/O218eVjrnc
Carrington around 1860: “long-term observations showed 11-year variability both in sunspot numbers and occurrence frequency of magnetic disturbances and auroras.” https://t.co/O218eVjrnc
“The geomagnetic activity connection to solar processes was established by mid-nineteenth century: Solar flare correlation with active, bright auroras and geomagnetic disturbances was found by Carrington in 1860.” https://t.co/O218eVjrnc
Anders Celcius and Olav Hiorter in 1747. “Comparing simultaneous magnetic variations in London and in Uppsala they further realized that the phenomena they were studying were related to processes in the planetary scale.” https://t.co/O218eVjrnc
“Anders Celcius and Olav Hiorter in 1747 discovered the temporal coincidence between compass needle variations and bright auroral displays.” https://t.co/O218eVjrnc
“The first steps of Sun-Earth connection science were made by Edmund Halley, who following the spectacular auroral displays in Europe in March 1716, suggested that particles moving along the Earth’s magnetic field lines were the cause of the aurora.” https
Space weather effects are also “critically dependent on the interaction of the impinging solar wind with the terrestrial magnetic field and plasma environment.” https://t.co/O218eVjrnc
Space weather. “Some effects are influenced neither by the properties of nor the processes within the Earth’s magnetosphere.” https://t.co/O218eVjrnc
“Space weather effects arise from the dynamic conditions in the Earth’s space environment driven by processes on the Sun.” https://t.co/O218eVjrnc