No abstract

There are reasons to believe that mechanisms exist in the solar interior which lead to random density perturbations in the resonant region of the Large Mixing Angle solution to the solar neutrino problem. We find that, in the presence of these density perturbations, the best fit point in the (sin 2 2θ, ∆m 2 ) parameter space moves to smaller values, compared with the values obtained for the standard LMA solution. Combining solar data with KamLAND results, we find a new compatibility region, which we call VERY-LOW LMA, where sin 2 2θ ≈ 0.6 and ∆m 2 ≈ 2 × 10 −5 eV 2 , for random density fluctuations of order 5% < ξ < 8%. We argue that such values of density fluctuations are still allowed by helioseismological observations at small scales of order 10 -1000 km deep inside the solar core.

We argue that solar neutrino observations have to be sensitive to the effects of magnetohydrodynamics fluctuations in the Sun if the resonant spin-flavor precession mechanism is the solution to the solar neutrino problem. We find that the required solar magnetic field for this solution presents global and localized magnetic waves with a typical period of the order of 1 to 10 days, which can generate a corresponding periodical time modulation of the solar neutrino observations. These effects can be thought of as a test to the spin-flavor precession solution. Periodicity of this order is not excluded by available experimental data although only with the high statistics of future real time experiments can a precise test be realized. We discuss also that these magnetic fluctuations can be used to obtain information about the structure of the magnetic field in the solar interior. ͓S0556-2821͑97͒05212-0͔ PACS number͑s͒: 96.60.Jw, 96.60.Hv

The theoretical properties of a composite chiral-plasma medium are developed. By using the reaction theorem for a magnetized chiroplasma, we obtain the proof of nonreciprocity based upon the constitutive relationships between electromagnetic vectors E, B, H, D. Using the Maxwelrs equations and the proposed constitutive relations for a chiral-plasma medium, we derive the vectors E and H and from these equations, dispersion relations and E-field polarizations are based. The obtained results for waves propagating parallel to the external magnetic field in a cold magnetized chiro-plasma are compared with typical results obtained for a cold plasma. For circulary polarized waves, a new mode conversion is founded with the chiral effect. The chiral rotation is obtained and compared with the Faraday rotation. For waves propagating across the magnetic field, we found a shift of the cutoffs of ordinary and extraordinary waves. On the lower branch of the extraordinary wave mode there is no bands of forbidden frequencies and the reflection point vanishes when the chiral parameter increases.

The standard 802.11 presents a MAC anomaly when the same Access Point operates stations with different data rates. Analysis shows that the degradation is higher for the station with a high data rate that operates with good signal to noise ratio (SNR). Consequently, the station with low SNR has higher throughput then stations with high SNR. To evaluate the anomaly an experimental test was created to obtain the WLAN behavior with wireless host transmitting with low SNR together with hosts with high SNR. The anomaly was evaluated experimentally utilizing two architectures: Fat and Thin. The anomaly was detected in the Fat architecture and was not detected in the Thin architecture. This paper presents a strategy to justify the result obtained with Thin architecture, using SNR to control the contention window and consequently mitigate the anomaly. Simulations using Network Simulator (NS) are presented to demonstrate the anomaly and to evaluate the mitigation anomaly strategy. The strategy configures the wireless stations with low SNR to work with large contention windows and wireless stations with high SNR with small contention windows. With this strategy the station with high SNR obtains higher throughput than the station with low SNR.