The interaction between the Moon and the solar wind

We study the interaction between the Moon and the solar wind using a three-dimensional hybrid plasma solver. The proton fluxes and electromagnetical fields are presented for typical solar wind conditions with different magnetic field directions. We find two different wake structures for an interplanetary magnetic field that is perpendicular to the solar wind flow, and for one that is parallell to the flow. The wake for intermediate magnetic field directions will be a mix of these two extreme conditions. Several features are consistent with a fluid interaction, e.g., the presence of a rarefaction cone, and an increased magnetic field in the wake. There are however several kinetic features of the interaction. We find kinks in the magnetic field at the wake boundary. There are also density and magnetic field variations in the far wake, maybe from an ion beam instability related to the wake refill. The results are compared to observations by the WIND spacecraft during a wake crossing. The model magnetic field and ion velocities are in agreement with the measurements. The density and the electron temperature in the central wake are not as well captured by the model, probably from the lack of electron physics in the hybrid model.Comment: Accepted for publication in Earth, Planets and Spac

Dynamics of solar wind protons reflected by the Moon

Solar system bodies that lack a significant atmosphere and significant internal magnetic fields, such as the Moon and asteroids, have been considered as passive absorbers of the solar wind. However, ion observations near the Moon by the SELENE spacecraft show that a fraction of the impacting solar wind protons are reflected by the surface of the Moon. Using new observations of the velocity spectrum of these reflected protons by the SARA experiment on-board the Chandrayaan-1 spacecraft at the Moon, we show by modeling that the reflection of solar wind protons will affect the global plasma environment. These global perturbations of the ion fluxes and the magnetic fields will depend on microscopic properties of the object's reflecting surface. This solar wind reflection process could explain past ion observations at the Moon, and the process should occur universally at all atmosphereless non-magnetized objects.Comment: 12 pages, 8 figure

Dopamine protects neurons against glutamate-induced excitotoxicity

Glutamate excitotoxicity is responsible for neuronal death in acute neurological disorders including stroke, trauma and neurodegenerative disease. Loss of calcium homeostasis is a key mediator of glutamate-induced cell death. The neurotransmitter dopamine (DA) is known to modulate calcium signalling, and here we show that it can do so in response to physiological concentrations of glutamate. Furthermore, DA is able to protect neurons from glutamate-induced cell death at pathological concentrations of glutamate. We demonstrate that DA has a novel role in preventing delayed calcium deregulation in cortical, hippocampal and midbrain neurons. The effect of DA in abolishing glutamate excitotoxicity can be induced by DA receptor agonists, and is abolished by DA receptor antagonists. Our data indicate that the modulation of glutamate excitotoxicity by DA is receptor-mediated. We postulate that DA has a major physiological function as a safety catch to restrict the glutamate-induced calcium signal, and thereby prevent glutamate-induced cell death in the brain

Klimatet och det urbana boendet: case Helsingfors : En kvalitativ fallstudie om den urbana styrningen av boendet och klimatet

Det råder inget tvivel om att urbana områden har en stor klimatpåverkan. Städer ses både som pådrivare, och som nyckelaktörer i bekämpningen av, klimatförändringar. För att garantera social och ekonomisk utveckling krävs ett säkert och stabilt klimat. Av denna anledning är klimatstyrning en av städernas viktigaste framtida uppgifter. Finlands befolkning blir allt mer urban, och därför är det av intresse att analysera sambandet mellan det urbana boendet och klimatförändringarna, och framför allt, hur den urbana styrningen av detta samband ser ut. Syftet med pro gradu-avhandlingen är att undersöka hur relationen mellan det urbana boendet och klimatet styrs, och mer specifikt analysera vilken roll staden har i styrningen. Empiriskt undersöks styrningen av, och sambandet mellan, det urbana boendet och klimatförändringarna, genom analys av valda styrdokument i fallstudieobjektet Helsingfors stad. Studien är således en kvalitativ innehållsanalys. Syftet med forskningen är att få en teoretisk snarare än statistisk generalisering av sambandet mellan, och styrningen av, urbant boende och klimatpolitiken. Det går inte att empiriskt visa att det är bättre för klimatet att bo urbant. Täthet borde erbjuda relativa fördelar för urbant boende, vilket det också till viss del tycks göra gällande de fysiska strukturerna kring boende och transport. Däremot bidrar den urbana livsstilen, präglad av välstånd, rörlighet och hög och parallell konsumtion, till att stadsbor ändå tycks ha en större inverkan på klimatet än de som bor på landsbygden. Helsingfors stads visioner för stadsutveckling vilar på expansion och förtätning, vilket uttrycks ha enbart positiva effekter på klimatet. I Helsingfors koncentreras styrningen av det urbana boendet och dess klimateffekter på boendets strukturella egenskaper, främst trafikplaneringen planering av markanvändning. Den urbana livsstilen fördubblar stadens utsläpp, men beaktas inte i klimatkalkylerna och därmed inte heller i de klimatpolitiska målen. Helsingfors försöker styra indirekta utsläpp genom att möjliggöra hållbara val. Styrningen av beteende sker till stor del genom skapandet av en tät stadsstruktur, som förväntas möjliggöra en klimatvänlig livsstil. Styrningen av Helsingfors, det urbana boendet och klimatet, sker genom flernivåsstyrning. Det finns en vilja och självupplevd syn av staden som ledare och samordnare av en bredare urban klimatpolitik. Staden har en central roll i styrningen av det urbana boendet, och dess effekter på klimatet

Protons in the near-lunar wake observed by the Sub-keV Atom Reflection Analyzer on board Chandrayaan-1

Significant proton fluxes were detected in the near wake region of the Moon by an ion mass spectrometer on board Chandrayaan-1. The energy of these nightside protons is slightly higher than the energy of the solar wind protons. The protons are detected close to the lunar equatorial plane at a $140^{\circ}$ solar zenith angle, i.e., ~50$^{\circ}$ behind the terminator at a height of 100 km. The protons come from just above the local horizon, and move along the magnetic field in the solar wind reference frame. We compared the observed proton flux with the predictions from analytical models of an electrostatic plasma expansion into a vacuum. The observed velocity was higher than the velocity predicted by analytical models by a factor of 2 to 3. The simple analytical models cannot explain the observed ion dynamics along the magnetic field in the vicinity of the Moon.Comment: 28 pages, 7 figure

The Fermi Surface Effect on Magnetic Interlayer Coupling

The oscillating magnetic interlayer coupling of Fe over spacer layers consisting of Cu$_{x}$Pd$_{1-x}$ alloys is investigated by first principles density functional theory. The amplitude, period and phase of the coupling, as well as the disorder-induced decay, are analyzed in detail and the consistency to the Ruderman-Kittel-Kasuya-Yoshida (RKKY) theory is discussed. For the first time an effect of the Fermi surface nesting strength on the amplitude is established from first principles calculations. An unexpected variation of the phase and disorder-induced decay is obtained and the results are discussed in terms of asymptotics

Mars Express/ASPERA-3/NPI and IMAGE/LENA observations of energetic neutral atoms in Earth and Mars orbit

The low energy neutral atom imagers on Mars Express and IMAGE have revealed that the neutral atom populations in interplanetary space come from a variety of sources and challenge our current understanding of heliospheric physics. For example, both in cruise phase and at Mars, the neutral particle instrument NPD on Mars Express observed "unexplained neutral beams" unrelated to Mars which appear to be either of heliospheric or solar wind origin. Likewise, the NPI instrument on Mars Express has revealed streams of neutral atoms with different properties than those observed by NPD. Independently, IMAGE/LENA has reported neutral atom observations that may be interpreted as a "secondary stream" having different characteristics and flowing from a higher ecliptic longitude than the nominal upstream direction. Both sets of observations do not appear to fit in easily with the neutral atom environment from 1.0-1.57 AU as it is currently understood. In this paper we examine some highly suggestive similarities in the IMAGE/LENA and Mars Express/ASPERA-3/NPI data to try to determine potential origins for the observed signal.Comment: in press Adv. Sp. Res., 15 pages, 9 figure

Laterality of motor activity during normal and disturbed sleep

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