Response time of the high-latitude dayside ionosphere to sudden changes in the north-south component of the IMF

1988 ◽  
Vol 36 (12) ◽  
pp. 1415-1428 ◽  
Author(s):  
H. Todd ◽  
S.W.H. Cowley ◽  
M. Lockwood ◽  
D.M. Willis ◽  
H. Lühr
Keyword(s):  
Response Time ◽  
High Latitude ◽  
The North ◽  
The Imf

Efficient carbon drawdown allows for a high future carbon uptake in the North Atlantic

2021 ◽  
Author(s):  
Nadine Goris ◽  
Jerry Tjiputra ◽  
Are Ohlsen ◽  
Jörg Schwinger ◽  
Siv Lauvset ◽  
...  
Keyword(s):  
North Atlantic ◽  
High Latitude ◽  
Deep Convection ◽  
Deep Ocean ◽  
Nutrient Supply ◽  
Global Ocean ◽  
Carbon Uptake ◽  
Model Ensemble ◽  
The North ◽  
The North Atlantic

<p>As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating and ameliorating the ongoing global warming. Projections of the North Atlantic carbon sink in a high-CO<sub>2</sub> future vary greatly among models, with some showing that a slowdown in carbon uptake has already begun and others predicting that this slowdown will not occur until nearly 2100.</p><p>Discrepancies among models largely originate because of differences in the efficiency of the high-latitude transport of carbon from the surface to the deep ocean. This transport occurs through biological production, deep convection and subsequent transport via the deep western boundary current. For an ensemble of 11 CMIP5-models, we studied the efficiency of this transport and identified two indicators of contemporary model behavior that are highly correlated with a model´s projected future carbon-uptake. The first indicator is the high latitude summer pCO<sub>2</sub><sup>sea</sup>-anomaly of a model, which is tightly linked to winter mixing and nutrient supply, but also to deep convection. The second indicator is the fraction of the anthropogenic carbon-inventory stored below 1000-m depth, indicating how efficient carbon is transported into the deep ocean. By comparing to the observational database, these indicators allow us to better constrain the model ensemble, and demonstrate that the models with more efficient surface to deep transport are best aligned with current observations. These models also show the largest future North Atlantic carbon uptake, which we then conclude is the more plausible future evolution. We further study if the high correlations between our contemporary indicators and a model´s future North Atlantic carbon uptake is also upheld for the next model generation, CMIP6. We hypothesize that this is the case and that our indicators can not only help us to constrain the CMIP6 model ensemble but also inform us about progress made between CMIP5 and CMIP6 in terms of North Atlantic carbon uptake, winter mixing, nutrient supply, deep convection and transport of carbon into the deep ocean.</p>

Explicit IMF By-dependence in geomagnetic activity

2021 ◽  
Author(s):  
Lauri Holappa ◽  
Timo Asikainen ◽  
Kalevi Mursula
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
High Latitude ◽  
Coupling Function ◽  
Future Space ◽  
Weather Modeling ◽  
Southern High Latitude ◽  
Imf Clock Angle ◽  
The Imf

<p>The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). Most solar wind coupling functions quantify this dependence on the IMF orientation with the so-called IMF clock angle in a way, which is symmetric with respect to the sign of the B<sub>y</sub> component. However, recent studies have shown that IMF B<sub>y</sub> is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for B<sub>y</sub> > 0 (B<sub>y</sub> < 0). For NH summer the dependence on the B<sub>y</sub> sign is reversed. We quantify the size of this explicit B<sub>y</sub>-effect with respect to the solar wind coupling function, both for northern and southern high-latitude geomagnetic activity. We show that for a given value of solar wind coupling function, geomagnetic activity is about 40% stronger for B<sub>y</sub> > 0 than for B<sub>y</sub> < 0 in NH winter. We also discuss recent advances in the physical understanding of the B<sub>y</sub>-effect. Our results highlight the importance of the IMF B<sub>y</sub>-component for space weather and must be taken into account in future space weather modeling.</p>

Machines and Media

2017 ◽  
Keyword(s):  
World War Ii ◽  
High Latitude ◽  
World War ◽  
Physics Laboratory ◽  
The North ◽  
The People ◽  
International Collaborations ◽  
Local Problems ◽  
Multiple Meanings

This chapter sets the stage for DRTE’s linking of nature and technology by examining anxieties about ionosondes — the chief instruments of ionospheric research. The ionosondes that emerged from World War II could not be trusted to capture rapidly-changing high-latitude phenomena. The chapter focuses on the efforts of Frank Davies and the Radio Physics Laboratory to create a coherent group of instruments, collectively responsible for mapping northern sectors of the global ionosphere. In doing so, it illustrates how efforts to standardize ionospheric equipment, as well as the multiple meanings of that standardization, opened up important possibilities for variation and difference in international collaborations. For Frank Davies and his group, the machines and the records they produced became a way of solving all-too-local problems with the North as a place of experiment and with the people occupying it.

scholarly journals Pathways of high-latitude dust in the North Atlantic

2017 ◽  
Vol 459 ◽  
pp. 170-182 ◽  
Author(s):  
Matthew C. Baddock ◽  
Tom Mockford ◽  
Joanna E. Bullard ◽  
Throstur Thorsteinsson
Keyword(s):  
North Atlantic ◽  
High Latitude ◽  
The North ◽  
The North Atlantic

Solar wind proton precipitation to the surface of Mercury

2020 ◽  
Author(s):  
Shahab Fatemi ◽  
Andrew R. Poppe ◽  
Stas Barabash
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
Solar Wind Dynamic Pressure ◽  
Solar Wind Proton ◽  
Entire Surface ◽  
The North ◽  
Proton Precipitation ◽  
Neutral Sodium ◽  
The Imf

<p>We examine the effects of the interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure on the solar wind proton precipitation to the surface of Mercury. We use the Amitis model, a three-dimensional GPU-based hybrid model of plasma (particle ions and fluid electrons), and explain a method we found necessary to accurately calculate plasma precipitation to the surface of Mercury through the highly dynamic Hermean magnetosphere. We use our model to explain ground-based telescope observations of Mercury's neutral sodium exosphere, and compare our simulation results with MESSENGER observations. For the typical solar wind dynamic pressure near the orbit of Mercury (i.e., ~7-8 nPa) our model shows a high solar wind proton flux precipitates through the magnetospheric cusps to the high latitudes on both hemispheres on the dayside with a higher precipitation rate to the southern hemisphere compared to the north, which is associated with the northward displacement of Mercury's intrinsic magnetic dipole. We show that this two peak pattern, which is also a common feature observed for neutral sodium exosphere, is controlled by the radial component (B<sub>x</sub>) of the IMF and not the B<sub>z</sub> component. Our model also suggests that the southward IMF and its associated magnetic reconnection do not play a major role in controlling plasma precipitation to the surface of Mercury through the magnetospheric cusps, in agreement with MESSENGER observations that show that, unlike the Earth, there is almost no dependence between the IMF angle and magnetic reconnection rate at Mercury. For the typical solar wind dynamic pressure, our model suggests that the solar wind proton precipitation through the cusps is longitudinally centered near noon with ~11<sup>o</sup> latitudinal extent in the north and ~21<sup>o</sup> latitudinal extent in the south, which is consistent with MESSENGER observations. We found an anti-correlation in the incidence area on the surface and the incidence particle rate between the northern and southern cusp precipitation such that the total area and the total rate through both of the cusps remain constant and independent of the IMF orientation. We also show that the solar wind proton incidence rate to the entire surface of Mercury is higher when the IMF has a northward component and nearly half of the incidence flux impacts the low latitudes on the nightside. During extreme solar events (e.g., Coronal Mass Ejections) a large area on the dayside surface of Mercury is exposed to the solar wind plasma, especially in the southern hemisphere. Our model suggests that over 70 nPa solar wind dynamic pressure is required for the entire surface of Mercury to be exposed to the solar wind plasma.</p>

scholarly journals The Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM): a parsimonious, satellite data-driven model of high-latitude CO<sub>2</sub> exchange

2015 ◽  
Vol 8 (2) ◽  
pp. 979-1027 ◽  
Author(s):  
K. A. Luus ◽  
J. C. Lin
Keyword(s):  
Eddy Covariance ◽  
North American ◽  
High Latitude ◽  
Growing Season ◽  
Growing Season Length ◽  
The North ◽  
Air Temperatures ◽  
High Latitude Region ◽  
Respiration Model ◽  
Photosynthesis And Respiration

Abstract. We introduce the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), a remote-sensing based approach for generating accurate, high resolution (≥1 km2, three-hourly) estimates of net ecosystem CO2 exchange (NEE). PolarVPRM simulates NEE using polar-specific vegetation classes, and by representing high-latitude influences on NEE. We present a description, validation, and error analysis (first-order Taylor expansion) of PolarVPRM, followed by an examination of per-pixel trends (2001–2012) in model output for the North American terrestrial region north of 55° N. PolarVPRM was validated against eddy covariance observations from nine North American sites, of which three were used in model calibration. PolarVPRM performed well over all sites. Model intercomparisons indicated that PolarVPRM showed slightly better agreement with eddy covariance observations relative to existing models. Trend analysis (2001–2012) indicated that warming air temperatures and drought stress in forests increased growing season rates of respiration, and decreased rates of net carbon uptake by vegetation when air temperatures exceeded optimal temperatures for photosynthesis. Concurrent increases in growing season length at Arctic tundra sites allowed increases in photosynthetic uptake over time by tundra vegetation. PolarVPRM estimated that the North American high-latitude region changed from a carbon source (2001–2004) to sink (2005–2010) to source (2011–2012) in response to changing environmental conditions.

Sign in / Sign up

Export Citation Format

Share Document