A comprehensive statistical study is conducted on O+ and H+ outflows obtained from the TEAMS/FAST data during the 23rd solar cycle (1996–2007). The study investigates interhemispheric asymmetry in ...ionospheric outflows during local summer, winter, and equinox seasons. Data are classified into two distinct periods: the pre‐storm and geomagnetic storm phases. Numerous statistical asymmetries are identified. The findings indicate that the dayside cusp consistently demonstrates more outflow rates of O+ and H+ in the northern hemisphere than southern hemisphere during geomagnetic storms in all seasons as well as during the pre‐storm period in the summer season with the exception of H+ during summer storms. Conversely, the nightside O+ and H+ outflow rates are higher in the southern hemisphere during pre‐storm and storm periods in the summer season. Additionally, the dawnside and duskside outflow rates of O+ and H+ are predominantly stronger in the southern hemisphere.
Plain Language Summary
The Earth's hemispheres receive different solar extreme ultraviolet radiation levels in different local seasons. In addition, there is a displacement between Earth's magnetic and geographic poles. Both mentioned factors cause interhemispheric asymmetries in ionospheric parameters. For the first time, this study investigates asymmetry in O+ and H+ ionospheric outflows between the northern and southern hemispheres by focusing on similar local seasons with comparable solar radiation levels. Data from the FAST/Time‐of‐flight Energy Angle Mass Spectrograph (TEAMS) instrument (1996–2007) are used for storms and pre‐storms. Hemispherical ionospheric outflows are categorized into summer, winter, and equinox and are spatially averaged in the polar regions. Findings reveal asymmetric ion outflows between hemispheres. The dayside cusp outflows are higher in the northern hemisphere than in the southern hemisphere during geomagnetic storms in all seasons except for H+ in summer. Conversely, nightside O+ and H+ outflows are more in the southern hemisphere than in the northern hemisphere during pre‐storm and storm periods in summer. Additionally, in dawnside and duskside, O+ and H+ outflows are predominantly stronger in the southern hemisphere than in the northern hemisphere.
Key Points
11‐year statistics find the northern and southern hemispheres exhibit asymmetric ion outflow even during similar local seasons
During storms, the cusp dayside exhibits higher O+ and H+ outflow rates in the northern hemisphere compared to the southern hemisphere
The dawnside and duskside O+ and H+ outflow rates are stronger in the southern hemisphere than in the northern hemisphere
The recalibrated FAST/TEAMS data is used to study the response of O+ and H+ outflow to energy inputs in the nightside aurora during the 24–25 September 1998 geomagnetic storm, the same storm studied ...by Strangeway et al. (2005), https://doi.org/10.1029/2004JA010829. In contrast to the cusp, the Poynting flux and electron precipitation energy input are not as well correlated on the nightside, so their effects on outflow can be differentiated. The O+ outflow shows a strong correlation with both the Alfvénic Poynting flux (r = 0.71) and the soft electron precipitation (r = 0.69), while the H+ outflow only correlates well with the electron number flux (r = 0.74). This indicates that the auroral H+ outflow is close to its limiting flux without additional wave acceleration, while the outflow for the heavier O+ ion is increased by additional wave acceleration.
Plain Language Summary
Geomagnetic activity can cause electrons to precipitate into the ionosphere in the nightside auroral region. It can also deliver electromagnetic wave energy to the same region. The electron precipitation can both heat and further ionize the ionosphere, leading to ions moving up along the field line. The wave energy can further accelerate the ions. If the ions are accelerated enough by these processes, they will flow out along the magnetic field, escaping the ionosphere. This paper finds that the H+ outflow increases with increased precipitating electrons in the nightside aurora. The O+ outflow increases with both electron precipitation and wave acceleration.
Key Points
Electron precipitation and Poynting flux are less correlated on the nightside than the cusp, so their effects on outflow can be distinguished
O+ outflow is correlated with both Poynting flux and electron precipitation, while H+ is only correlated with electron precipitation
Parameterization of the outflow dependence is consistent between the dayside cusp and the nightside auroral regions
Factors related to two sources of energy input to the ionosphere, the Poynting flux associated with both quasistatic fields (Sdc) and Alfvénic fluctuations (Sac), and the soft electron precipitation, ...are investigated to evaluate their correlations with the O+ and the H+ outflows in the dayside cusp region by using recalibrated FAST/Time‐of‐Flight Energy, Angle, and Mass Spectrograph (TEAMS) data during the 24–25 September 1998 geomagnetic storm studied by Strangeway et al. (2005, https://doi.org/10.1029/2004JA010829). The Poynting flux and the soft electron precipitation are well correlated with ion outflow flux in the dayside cusp region. Sdc shows the highest correlation with the O+ outflows, while it is the electron number flux that correlates best with the H+ outflows. The Alfvénic waves play an essential role in accelerating outflows. The averaged O+/H+ flux ratio is 3.0 and is positively correlated to the Poynting flux, suggesting that the O+ flux increases more strongly with the energy input.
Plain Language Summary
Ionospheric outflows are a major plasma source for the Earth's magnetosphere, especially during geomagnetic storms. Various parameters related to the electromagnetic energy input, the electron precipitation, and the extremely low frequency plasma waves are used to investigate their correlations with ion outflows in the dayside cusp region during the 24–25 September 1998 geomagnetic storm. We first recalibrated the data from the FAST/Time‐of‐Flight Energy, Angle, and Mass Spectrograph (TEAMS) instrument before using it. The electromagnetic energy has the highest correlations with the oxygen ion outflows, while it is the electron precipitation for proton outflows. The energy input associated with Alfvén waves also shows strong correlations. Maxima of the energy input show better correlations than the averages. The oxygen ion is the dominant outflow species in this storm with an average flux ratio of 3.0 to proton outflows. A higher ratio is observed with more energy input to the Earth's ionosphere.
Key Points
The best controlling factor for driving O+ and H+ outflows is quasistatic Poynting flux and soft electron precipitation, respectively
The averaged O+/H+ flux ratio is 3.0 over the cusp region. The ratio is positively correlated to energy input to the ionosphere
The Poynting flux associated with Alfvén waves also shows strong correlation with outflows in the dayside cusp region
In this study, a simple and efficient method for the formation of carbon–sulfur bonds is described. In this process, ring opening of maleic anhydride by thiols or disulfides and triphenylphosphine ...led to the formation of sulfide products via formation of two carbon-sulfur bonds.
In this study, a simple and efficient method for the formation of carbon-sulfur bonds is described. In this process, ring opening of maleic anhydride by thiols or disulfides and triphenylphosphine ...led to the formation of sulfide products
formation of two carbon-sulfur bonds.
Geomagnetic storms are primarily driven by stream interaction regions (SIRs) and coronal mass ejections (CMEs). Since SIR and CME storms have different solar wind and magnetic field characteristics, ...the magnetospheric response may vary accordingly. Using FAST/TEAMS data, we investigate the variation of ionospheric O+ and H+ outflow as a function of geomagnetic storm phase during SIR and CME magnetic storms. The effects of storm size and solar EUV flux, including solar cycle and seasonal effects, on storm time ionospheric outflow, are also investigated. The results show that for both CME and SIR storms, the O+ and H+ fluences peak during the main phase, and then declines in the recovery phase. However, for CME storms, there is also significant increase during the initial phase. Because the outflow starts during the initial phase in CME storms, there is time for the O+ to reach the plasma sheet before the start of the main phase. Since plasma is convected into the ring current from the plasma sheet during the main phase, this may explain why more O+ is observed in the ring current during CME storms than during SIR storms. We also find that outflow fluence is higher for intense storms than moderate storms and is higher during solar maximum than solar minimum.
Key Points
Both coronal mass ejection (CME) and stream interaction region (SIR) storms have their maximum O+ and H+ outflow during the main phase, and a decrease during the recovery phase
During CME storms, the outflow increases during the initial phase, while during SIR storms it doesn’t increase until the main phase
This difference in outflow timing may explain why more O+ is observed in the ring current during CME storms than during SIR storms
On the Role of Ionospheric Ions in Sawtooth Events Lund, E. J.; Nowrouzi, N.; Kistler, L. M. ...
Journal of geophysical research. Space physics,
January 2018, 2018-01-00, 20180101, Letnik:
123, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Simulations have suggested that feedback of heavy ions originating in the ionosphere is an important mechanism for driving sawtooth injections. However, this feedback may only be necessary for events ...driven by coronal mass ejections (CMEs), whereas in events driven by streaming interaction regions (SIRs), solar wind variability may suffice to drive these injections. Here we present case studies of two sawtooth events for which in situ data are available in both the magnetotail (Cluster) and the nightside auroral region (FAST), as well as global auroral images (IMAGE). One event, on 1 October 2001, was driven by a CME; the other, on 24 October 2002, was driven by an SIR. The available data do not support the hypothesis that heavy ion feedback is necessary to drive either event. This result is consistent with simulations of the SIR‐driven event but disagrees with simulation results for a different CME‐driven event. We also find that in an overwhelming majority of the sawtooth injections for which Cluster tail data are available, the O+ observed in the tail comes from the cusp rather than the nightside auroral region, which further casts doubt on the hypothesis that ionospheric heavy ion feedback is the cause of sawtooth injections.
Key Points
We present in situ observations from tail and nightside auroral region of two sawtooth events, one CME‐driven and one SIR‐driven
We find no evidence in either event that heavy ion feedback drives sawtooth injections
Results agree with simulation results for SIR‐driven event but not CME‐driven event
Abstract Previous simulations have suggested that O + outflow plays a role in driving the sawtooth oscillations. This study investigates the role of O + by identifying the differences in ionospheric ...outflow between sawtooth and non‐sawtooth storms using 11 years of FAST/Time of flight Energy Angle Mass Spectrograph (TEAMS) ion composition data from 1996 through 2007 during storms driven by coronal mass ejections. We find that the storm's initial phase shows larger O + outflow during non‐sawtooth storms, and the main and recovery phases revealed differences in the location of ionospheric outflow. On the pre‐midnight sector, a larger O + outflow was observed during the main phase of sawtooth storms, while non‐sawtooth storms exhibited stronger O + outflow during the recovery phase. On the dayside, the peak outflow shifts significantly toward dawn during sawtooth storms. This strong dawnside sector outflow during sawtooth storms warrants consideration.
Plain Language Summary A sawtooth event is a convection mode in Earth's magnetosphere, which transports solar wind plasma and energy into the inner magnetosphere and ionosphere. Despite three decades since their discovery, the mechanism behind sawtooth oscillations remains uncertain. One theory suggests that O + outflow induces sawtooth oscillations through an internal feedback mechanism. In line with this theory, some simulations have generated sawtooth oscillations under steady geomagnetic conditions. Furthermore, previous observations indicate that some, but not all, geomagnetic storms exhibit sawtooth oscillations. This study utilizes data from the FAST/TEAMS instrument (1996–2007) and compares O + outflow variations during geomagnetic storms with and without sawtooth oscillations. Findings indicate that during the storms' initial phase, sawtooth storms produce less O + outflow than non‐sawtooth storms. Additionally, non‐sawtooth storms exhibit higher O + outflow in the dayside during the main phase and in the pre‐midnight sector during the recovery phase, challenging the key role of O + outflow in driving the feedback mechanism. However, observing large O + outflow in the dawnside sector of sawtooth events suggests more investigation is needed.
Key Points The intensity and location of O + outflow during storms are different in storms with and without sawtooth oscillations The peak dayside outflow is significantly shifted toward dawn during storms with sawtooth observations The nightside picture is mixed; the pre‐midnight O + outflow is higher in the main phase but lower in the recovery phase of sawtooth storms
In this study, a simple and efficient method for the formation of carbon-sulfur bonds is described. In this process, ring opening of maleic anhydride by thiols or disulfides and triphenylphosphine ...led to the formation of sulfide products
via
formation of two carbon-sulfur bonds.
Synthesis of
S
-aryl-3-(arylthio)propanethioate from the reaction of maleic anhydride and thiolic compounds in the presence of Ph
3
P.
An efficient, inexpensive and reusable NiCl 2 ·6H 2 O/ n -Bu 4 NBr catalytic system is described for the direct C–H arylation of 2-hydroxybenzaldehydes with aryl iodides for the first time.
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