More than 140 isolated non-recurrent geomagnetic storms (GMSs) of various intensities from extreme to weak are considered; these are reliably identified with solar eruptive sources (coronal mass ...ejections, CMEs). The analysis aims to obtain a possibly complete picture of the relationship between the transit time of propagation of CMEs and interplanetary coronal mass ejections (ICMEs) from the Sun to the Earth (more precisely, the time interval
Δ
t
p
from the moment of an eruption until the peak of the corresponding GMS) and the maximum intensity of this GMS, as measured by the disturbance storm time geomagnetic index Dst. Two groups of events are singled out: one includes GMSs, the source of which was an eruption from an active region (AR events), the other GMSs caused by filament eruptions from quiescent areas of the Sun located outside ARs (QS events). The distribution of the large number of the analyzed events on a
Δ
t
p
– Dst plane confirms and substantially clarifies the known regularities. The AR events are characterized by a shorter transit time (
Δ
t
p
≈
1
–4 days) and much stronger GMSs (Dst up to –600 nT mainly) in comparison with the QS events (
Δ
t
p
≈
3
–5 days, Dst > –200 nT). For events of both groups, the shorter the transit time of CMEs/ICMEs, the more intense the GMSs; in particular, for AR events when
Δ
t
p
declines from 4 to 1 day, Dst decreases on average from –100 to –470 nT and can reach – 900 nT. From the point of view of the nature of GMSs and their sources on the Sun, the obtained results mean that both the speed of CMEs/ICMEs and the strength of the magnetic field transported by them are largely determined by the parameters of the corresponding eruptions, in particular, by the eruptive magnetic flux and the released energy.
ABSTRACT
In addition to several recent articles devoted to the rare event of ground-level enhancement of the solar relativistic proton flux observed on 2021 October 28 – GLE73, we study the 10–100 ...MeV solar energetic particle (SEP) component of this event. Based on the Geostationary Operational Environmental Satellite data for 26 GLEs recorded since 1986, we have formed a scatter plot displaying the ratio of the peak fluxes of the $\gt $10 MeV ($J_{10}$) and $\gt $100 MeV ($J_{100}$) protons and their energy spectra. Two extreme characteristics of the prompt component of the SEP–GLE73 event were revealed: (1) very small $J_{10}$ and $J_{100}$ proton fluxes and (2) a very hard energetic spectrum in the 10–100 MeV range. There are only two events with these characteristics similar to SEP–GLE73, namely GLE40 (1989 July 25) and GLE46 (1989 November 15). A correspondence was demonstrated between the hard frequency spectrum of microwave radio bursts of initiating flares and the hard SEP energy spectrum of these two and other GLEs. These results suggest that the flare magnetic reconnection both in the impulsive and post-eruption phases plays an important role in the acceleration of the SEP–GLE protons.
Biomicroscopy was used to study order I-IV branches of the uterine artery in sexually mature female Wistar rats after a single 5- or 10-min direct exposure of the right broad ligament of the uterus ...to a helium-neon laser beam in the red band of the spectrum (λ=632.8 nm, output power 2 mW, intensity 20 mW/cm
2
). Under the influence of laser exposure, there was a significant increase in the diameter of small uterine branches and a weaker increase in large vessels with a well-developed muscular membrane. Preliminary administration of zinc IX protoporphyrin hemoxygenase blocker (30 mmol/kg) reduced reactivity of the vascular bed to laser irradiation, mainly of order I-II branches. It was concluded that carbon monoxide can act as an intermediary between the laser exposure and uterine vessels.
The quantitative content of HIF-1α- and HIF-2α-immunopositive brain neurons in Wistar rats was studied 1, 15, and 30 days after modeling of myocardial infarction. In rats of the control group, the ...immunohistochemical markers HIF-1α and HIF-2α in the prefrontal cortex of the brain were determined in few pale-colored neurons and capillaries. One day after myocardial infarction simulation, the number of HIF-1α
+
neurons increased, and on day 15 it reached the maximum level: the concentration of immunopositive neurons and capillaries increased by 24.7 and 18.4%, respectively, in comparison with the control. After 30 days, the number of HIF-1α
+
structures decreased, but remained above the control values. The number of neurons and capillaries positively stained for HIF-2α peaked only on day 30 of the postinfarction period.
Based on our tool for the early diagnostics of solar eruption geoeffectiveness (EDSEG tool; Chertok et al., 2013, https://doi.org/10.1007/s11207‐012‐0127‐1; 2015, ...https://doi.org/10.1007/s11207‐014‐0618‐3; 2017, https://doi.org/10.1007/s11207‐017‐1081‐8), we have analyzed space weather disturbances that occurred in early September 2017. Two flares, SOL2017‐09‐04T20:33 (M5.5) and SOL2017‐09‐06T12:02 (X9.3), accompanied by Earth‐directed halo coronal mass ejections (CMEs) were found to be geoeffective. We extracted the associated extreme ultaviolet dimmings and arcades and calculated their total unsigned magnetic flux. This calculation allowed us to estimate the possible scales of the Forbush decreases (FDs) and geomagnetic storms (GMSs) in the range from moderate to strong, and they are close to the observed scales. More precisely, after the first eruption, an FD approximately equal to 2% and almost no GMS occurred because the Bz magnetic field component in front of the corresponding interplanetary CME (ICME) was northern. The stronger second eruption produced somewhat larger composite disturbances (FD ≈ 9.3% and GMS with indexes Dst ≈ −144 nT, Ap ≈ 235) than expected (FD ≈ 4.4%, Dst ≈ −135 nT, Ap ≈ 125) because the second ICME overtook the trailing part of the first ICME near Earth, and the resulting Bz component was more intense and southern. Both ICMEs arrived at Earth earlier than expected because they propagated in the high‐speed solar wind emanated from an extended coronal hole adjacent to the active region AR12673 along their entire path. Overall, the presented results provide further evidence that the EDSEG tool can be used for the earliest diagnostics of actual solar eruptions to forecast the scale of the corresponding geospace disturbances.
Plain Language Summary
Space weather nonrecurrent disturbances such as geomagnetic storms and Forbush decreases of galactic cosmic rays are caused by coronal mass ejections that erupt from the Sun and propagate to Earth. We analyze such disturbances in connection with an outstanding outburst of solar flare activity that occurred at the beginning of September 2017 and compare their parameters with estimates from our tool for the early diagnostics of solar eruption geoeffectiveness. The estimates are based on measurements of the magnetic flux of the earliest coronal mass ejection manifestations in the extreme ultraviolet range such as bright coronal posteruptive arcades and areas with temporarily reduced brightness (so called dimmings). We demonstrate that this tool yields the earliest relatively correct estimates for the scales of geomagnetic storm and Forbush decreases despite the complexity of the near‐Earth solar wind structures in September 2017.
Key Points
The total magnetic flux of the EUV arcades and dimmings of two solar eruptive flares from early September 2017 is used for geoeffectiveness diagnostics
The estimated scales of the space weather disturbances caused by the flares are close to those of the observed Forbush decreases and geomagnetic storms
The roles of a high‐speed stream from an adjacent coronal hole and the interaction between two ICMEs near Earth are considered
On the approach to minimum of Solar Cycle 24, on 26 August 2018, an unexpectedly strong geomagnetic storm (GMS) suddenly occurred. Its
D
st
index reached
−
174
nT
, that is, the third most intense ...storm of the cycle. The analysis showed that it was initiated by a two-step long filament eruption, which occurred on 20 August in the central sector of the solar disk. The eruptions were accompanied by two large-scale divergent flare-like ribbons and dimmings of a considerable size and were followed by relatively weak but evident Earth-directed coronal mass ejections. In the inner corona, their estimated speed was very low, about
200
–
360
km
s
−
1
. The respective interplanetary transients apparently propagated between two high-speed solar wind streams originated from a two-component coronal hole and therefore their expansion was limited. The resulting ejecta arrived at Earth only on 25 August and brought an unexpectedly strong field of
B
t
≈
18.2
nT
with a predominantly negative
B
z
component of almost the same strength. The geospace storm also manifested itself in the form of a peculiar Forbush decrease (FD). Its magnitude was about 1.5%, which is rather small for the observed G3-class GMS. The main unusual feature of the event is that large positive bursts with an enhancement up to 3% above the pre-event level were recorded on the FD background. We argue that these bursts were mainly caused by an unusually large and changeable cosmic ray anisotropy combined with lowering of the geomagnetic cutoff rigidity in the perturbed Earth’s magnetosphere under cycle minimum-like conditions.
The powerful solar flares that occurred on September 4–10, 2017 are analyzed based on a quantitative diagnostics method for proton flares developed at the Institute of Terrestrial Magnetism, the ...Ionosphere and Radio-Wave Propagation (IZMIRAN) in the 1970–1980s. We show that the fluxes and energy spectra of the protons reached the Earth with the energies of tens of MeV qualitatively and quantitatively correspond to the intensity and frequency spectra of the microwave radio bursts in the range of 2.7–15.4 GHz. Specifically, the flare of September 4 with a peak radio flux
S
~ 2000 sfu at the frequency
f
~ 3 GHz (i.e., with the soft radio spectrum) was accompanied by a significant proton flux
J
(>10 MeV) ~100 pfu and a soft energy spectrum with the index γ ~3.0, while the strong flare on September 10 with
S
~ 21000 sfu at
f
~ 15 GHz (i.e., with the hard radio spectrum) led to a very intense proton event with
J
(>10 MeV) ~1000 pfu with a hard spectrum (γ ~ 1.4), including the ground level enhancement (GLE72). This is further evidence that microwave radio data can be successfully used in diagnostics of proton flares independently of a specific source of particle acceleration at the Sun, in particular, with the IZMIRAN method.
We present a case study of the 13 July 2004 solar event, in which disturbances caused by eruption of a filament from an active region embraced a quarter of the visible solar surface. Remarkable are ...the absorption phenomena observed in the SOHO/EIT 304 Å channel, which were also visible in the EIT 195 Å channel, in the Hα line, and even in total radio flux records. Coronal and Moreton waves were also observed. Multispectral data allowed reconstructing an overall picture of the event. An explosive filament eruption and related impulsive flare produced a CME and blast shock, both of which decelerated and propagated independently. Coronal and Moreton waves were kinematically close and both decelerated in accordance with an expected motion of a coronal blast shock. The CME did not resemble a classical three-component structure, probably because some part of the ejected mass fell back onto the Sun. Quantitative evaluations from different observations provide close estimates of the falling mass, ∼3×10
15
g, which is close to the estimated mass of the CME. The falling material was responsible for the observed large-scale absorption phenomena, in particular, shallow widespread moving dimmings observed at 195 Å. By contrast, deep quasi-stationary dimmings observed in this band near the eruption center were due to plasma density decrease in coronal structures.
This review presents data on the cellular-molecular mechanisms regulating angiogenesis associated with the vascular endothelium. Existing concepts hold that the control of angiogenesis involves ...activated endothelial cells and their precursors (progenitor cells), which synthesize and release angiogenic molecules with different chemical structures and mechanisms of biological action, but all allowing these cells to control each stage of angiogenesis directly or indirectly. Balanced functioning of the system of molecular stimulators and inhibitors of angiogenesis is particularly important for the brain, as excessive formation of blood vessels, like inadequate development of blood vessels, leads in certain conditions to rapid and irreversible changes in nervous tissue. Post-operative neurorepair cannot occur without adequate reperfusion of the injured part of the brain, which can be supported by timely stimulation of angiogenesis, while intensification of this process in tumors, conversely, has adverse consequences. Tumor growth and metastasis are significantly linked with increases in the level of vascularization of malignant tissue, while blockade of angiogenesis is not infrequently the only productive method of limiting tumor growth. However, we have insufficient knowledge of the mechanisms regulating angiogenesis in the brain at the cellular-molecular level in physiological conditions and pathology, so angiogenic influences do not always produce the expected effect.
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