Friday, September 26, 2008

Solar System shield lowering increasing Galactic Cosmic ray flux

The ESA and Nasa have issued a joint statement on the decreasing solar wind output.

23 September 2008
Data from the joint ESA/NASA Ulysses mission show that the Sun has reduced its output of solar wind to the lowest levels since accurate readings have become available. This current state of the Sun could reduce the natural shielding that envelops our Solar System.

"The Sun’s 1.5 million km-per-hour solar wind inflates a protective bubble around the Solar System and can influence how things work here on Earth and even out at the boundary of our Solar System, where it meets the galaxy," said Dave McComas, Principal Investigator for the Ulysses solar wind instrument and senior Executive Director at the Southwest Research Institute in San Antonio, Texas. "Ulysses data indicate the solar wind’s global pressure is the lowest we have seen since the beginning of the space age."

The Sun's solar wind plasma is a stream of charged particles that are ejected from the upper atmosphere of the Sun. The solar wind interacts with every planetary body in our Solar System. It even defines the border between our Solar System and interstellar space.

This border, called the heliopause, is a bubble-shaped boundary surrounding our Solar System where the solar wind's strength is no longer great enough to push back the wind originating from other stars. The region around the heliopause also acts as a shield for our Solar System, warding off a significant portion of the cosmic rays outside the galaxy.

Galactic cosmic rays carry with them radiation from other parts of our galaxy," said Ed Smith, NASA's Ulysses Project Scientist from the Jet Propulsion Laboratory in California, USA. "With the solar wind at an all-time low, there is an excellent chance that the heliosphere will diminish in size and strength. If that occurs, more galactic cosmic rays will make it into the inner part of our Solar System."

This is evident in the Moscow neutron graph in the previous post..There we see the topology of the peak/plateau modulation in the odd/ even solar cycles, and seen in the idealized mathematical model above.

The 22-year cycle is seen in the GCR intensity, since during solar cycles with negative polarity of the Sun’s northern polar field (field is directed into the Sun) cosmic-ray time dependence has a peaked form and during cycles with positive polarity (field is directed out of the Sun) it has a plateau form. Such an effect is caused by the difference in cosmic ray drift directions during positive and negative phases of the magnetic cycle. The time behavior of galactic proton flux was theoretically investigated by Jokipii (1991)

It is evident that integrated cosmic-ray flux during the plateau phase of the cycle is twice as large as during the peaked phase. Clearly, if the Earth’s atmosphere reacts effectively to the cosmic-ray flux integrated over the corresponding cycle, appreciable bidecadal variation in climate may arise. This variation should be more pronounced at high latitudes, because cosmic rays are more intense in the polar regions.This is indeed the case with high levels of Nox over the south pole.

M. G. OGURTSOV et al explain the causal mechanisms.

Optical mechanism, which takes into account changes of atmospheric transparency
caused by changes in fluxes of galactic cosmic rays (GCR) and solar cosmic rays (SCR), consisting mainly of energetic protons (energies up to few GeV), can reach even the Earth’s surface. Their fluxes change substantially with solar activity and can influence atmospheric opacity in two ways. The first is connected with the changes in atmospheric chemistry. The SCR and GCR particles react with N2 and O2, which lead to their dissociation and ionization. Ions of N+2 ,O+2 , N+, O+ are formed and they are involved in a complex of photochemical reactions, which produce nitrogen oxide, NO. NO and atomic oxygen O effectively destroy ozone. Hence, the input of high-energy particles into the atmosphere causes destruction of ozone and the generation of NO2 (Pudovkin and Raspopov, 1992). Such changes are particularly strong during proton events. For example, on 4 August of 1972, at 30–35 km altitude, the concentration of ozone decreased ten times and the concentration of NO2 increased by factor 2. Inasmuch as NO2 absorbs intensively solar radiation in the green and blue part of the spectrum, the irradiance at the Earth’s surface decreases. Ultraviolet flux increases, due to ozone depletion of the stratosphere, and the radiation balance of the atmosphere changes, which may result in changes in atmospheric circulation. It should be noted that ozone depletion probably leads to the cooling of the Earth’s surface, because the greenhouse effect of ozone exceeds the effect of UV heating (Larin, 2002). Thus, besides changes in the circulation pattern, variation in the chemical composition of the atmosphere, caused by input of energetic particles, can cool the lower troposphere. A change of the temperature altitude profile in the atmosphere, caused by high-energy particles, is described by Pudovkin and Dementeeva (1997).

The times they are a changing.


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